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Full text of "Carrying capacity of the Ichetucknee Springs and River"

n^m^ 



THE CARRYING CAPACITY OF THE ICHETUCKNE2 SPRINGS AND RIv^R 



BY 
CHARLES H. DUTOIT 



A THESIS PJIESENTED TO THE GRADUATE COUNCIL OF THE 

UNIVERSITY OF FLORIDA 

IN PARTIAL FULFILLr-lENT OF THE P:EQUIFlE>ENT3 FOR TEE 

DEGREE OF MASTER OF SCIENCE 



UNIVERSITY OF FLORIDA 
1979 



ACKNOWLEDGEMENTS 

I would like to thank my conunittee members, Dr. Frank 
Nordlie and Dr. Ariel Lugo, for their help and interest in 
the research, as well as Dr. Gordon Godshalk, who reviewed 
the manuscript . 

This research was a result of the concern and orelimi- 
nary work of Dr. John Ewel, my chairman. Dr. Ewel's guidanc: 
was fundamental to the design of the study, its implementa- 
tion, and write-up. 

The Florida Department of Naxural Resources, the asrency 
( which administers Ichetucknee Springs State Park, not only 
provided a comfortable working atmosphere , but also directly 
assisted in the study by constructing fenced exclosures and 
cages. I greatly appreciate Major Hardee's cooperation, and 
an grateful to Captain Krause and Captain Barrer, as well as 
the entire staff, for installing the underwater structures 
and helping me in innumerable ways. I thank Lt . Don Younker 
for arranging and participating in visits by university and 
DNR personnel . 

A number of University of Florida students assisted in 
the research. I -hank Joe Vargo and Bob Rice for the hours 
they spent in the water, and Ellen Kane for the hours she 
spent at the plan.im.e-ry table. 1 was also ably assisted in 



both the field and lab by the followirxg students: Charner 
Benz, Karen Hokkanen , Doran Pace, David Sample, Barbara 
Harris, John Goelz , Patty Kohnke, Robert Somes, and Brian 
LaPointe . 

I was short of help on several occasions. I am grate- 
ful to those individuals who assisted at such times; Dennis 
Ojima, a fellow graduate student, and the following members 
of the Gainesville chapter of the Sierra Club: Ken Watson, 
Steve Dalton, Kathy Haseman, William Girnat , Otho Feterman, 
and Tim Pollack. 

Alma Lugo and Gary Daught drafted the figures, Joan 
Crisman t37ped the manuscript, and Marilyn DuToit prepared 
the plant communities map. 

The research contained in this thesis was supported 
by a research grant to the University of Florida: "Carrying 
Capacity of the Ichetucknee Springs and River System," 
P. 0. 106 38, J, Ewel, Principal Invesxigator . 



11 



v: 



VI 1 



CONTENTS 

ACKlNlOWLEDGEMENTS . . ' 

LIST OF TABLES 

LIST OF FIGURES 

LIST OF COLOR PLATES x 

ABSTRACT .' ^^ 

INTRODUCTION 1 

Geology 1 

Hydrology . . . , 3 

Water Quality '. ] 5 

Morphology of the Ichetucknee Rivar ,* .' 5 

Vegetation . . . . 7 

Natural History 7 

Cultural History _ g 

History of Recreational Use . '. 10 

Profile of Park Users ] 11 

The Carrying Capacity Concept 13 

OBJECTIVES i_g 



METHODS 







Base Map 2 

Standing Crop 21 - 

Plant Damage Survey 9i 

Plant Resistance 2U- 

Changes in Plant Cover 2^ 

Plant Recovery ] _' 2U- 

Response to Repeated Cutxing 31 

Fauna Survev Z' /" 

RESULTS 2!4 

Base Map '. '. ' ' 34 

Types and Amounts of Recreational Use 35 

Plant Damage Survey ! .* .' 3 7 

Planx Resistance c^ 

Changes in Plant Cover [ ^ SI - 

Ex-oerimenta'' °lr-.t=; c- 

ixciosures . , pp 

Blue Hole Cages , . 7 5 

Response to Reoeated Cutrin'^ 7q 

Fauna Survev si - / 

"^ V 

iv 



CONTENTS 
(Continued) 



DISCUSSION 88 

Impact of Recreation on the Plant Communities 

of the Headsprings Reach 3 3 

Impact of Recreation on the Plant Communities 

of the Rice Marsh and Floodplain Reach 112 

Impact of Recreation on the Animals of 

the River 12M- V 

The Carrying Capacity for Recreation 12 



o n 



LITERATURE CITED , 13 9 

APPENDICES 

A. METHODS OF INDIRECT MEASUREMENT l4 2 

A-1. PERCENTAGE DRY WEIGHT OF 

NETTED PLANTS, PLANT DAiMAGE SURVEY, 

SUMMER, 1973 142 

A-2. RELATIONSHIP OF CLUMP 3I0MASS Ai^'D 
LENGTH OF LONGEST LEAF, 
Sagittaria kurziana l44 

A- 3. RELATIONSHIP OF LEAF WEIGHT 
AND LEAF LENGTH, 
Sagittaria kurziana 14-5 

k-^. INDIRECT A!ID DIRECT MEASUREMENT 
OF PLANT 3I0'4.^SS IN 
EXPERIMENTAL PLOTS l-'l5 

B„ A-MOUNTS OF HOURLY USE AND DAMAGE, 
BY SPECIES, PLANT D.^^MAGE SURVEY, 
SUMMER, 19 73 14? 

C. BIOMASS OF ACUATIC PLANTS OF THE 

ICKETUCKNEE RIVER 15 4 

D. STANDING CROP OF AQUATIC PLANTS IN THREE 

xRE ACHES OF THE ICHETUCKNEE RIVER 156 - 

E. PLANT COMMUNITIES OF THE ICHETUCKNEE RIVER, , . 157 - 
BIOGP^A.PHICAL SKETCH 17 6 



LIST OF TABLES 
Table 

1. Water quality of the Ichetucknee Springs 6 

2. Common species of the plant communities 

of the Ichetucknee Springs State Park 8 

3. Regrowth of aquatic plants following 

cutring or uprooting , 5 7 

M- . Plant biomass and the number and weight 
of invertebrates sampled in three areas 
subject to varying degrees of recreational 
disturbance 8 2 

5. Types and numbers of fish in disturbed 
(First Dock area) and undisturbed 
CHeadsprings Exclosure) sections of the 
Headsprings Reach 3 5 

6. Recommended carrying capacities 128 



VI 



LIST OF FIGURES 



Figure 



1. Map of Ichetucknee Springs State Park 2 

2. Annual park attendance, 1973-74 to 1977-73 ... 12 

3 . Location of netting stations and 

experimental plots ..... 23 

M- . Location of fenced exclosures , Tnap-remaTD 

sections, and fauna survey sites ...'..... 25 

5. Location of cages in the Blue Hole 2 9 

6. Types and amounts of recreational use, 
January-August, 1978 .. 3 6 

7- Winter plant damage related to total number 

of users and to number of divers 3 8 

8. Damage, by species, related to number of 

divers, Winter, 1977-78 40 

9. Percent total damage and percent of total 
standing crop of species netted in 

Winter, 1977-78 43 

10. Amounts of daily planr damage and daily use 

in three reaches. Summer, 1978 45 

11. Amounts of hourly plant damage and use in 

three reaches, Summer, 19^^ 8,, 47 

12. Number of users and fractional loss 
of standing crop, for three reaches. 

Summer, 19 7 8 \ 4 8 

13. Percent total damage and percent total 
standing crop for plant species in . ^ 

three reaches. Summer, 19 7 8 50 i 



VI 1 



LIST OF FIGURES 
(Continued) 



Figure 



14-. Resistance to tearing and uprooting 52 

15. Seasonal changes in plant cover in three 

sections of the Headsprings Run 5 3 

IS. Standing crop and recovery of Sagittaria 

leaves following cutting 5 

17. Standing crop and clump recovery of 

Sagittaria following uprooting 6 

18. Number of Sagittaria clumps counted in 
quadrats following uprooxing, and standing 
crop (no. of clumps) in undisturbed quad- 
rats sampled in February and June, 1973 51 



19 



?3 



Standing crop and regrowth of Myriophyllum 
following cutting '. . ~t ! '. T . . . SS 



20. Change in plant cover, Site A, Headsprings 
txclosure, 6-12-78 to 3-2U-78 B7 

21. Change in channel profile, Site B, Headsprings 
Exclosure, 8-3-78 to 10-12-78 '. .\ . 71 

22. Change in plant cover, Second Dock ,.-■:: 
Exclosure, ':'-25-78 to 10-26-78 72 



Growth of Zizania and Chara , Second 

Dock Exclosure 74 



24. Characteristics of Sagittaria leaves sampled 

both inside and outside of Jug Cage. ..".... 76 

25. Sagittaria colonization and characteristics 
of leaves sampled inside and outside of 

the Run Cage 73 

26. Sagittaria leaf recovery in plots 

subjected to repeated cutting 80 



27, Amounts of daily use and plant damage, 

Headsprings Reach, Summ.er, 1978. . ? 90 



Vlll 



■i"«(W-WI 



LIST OF FIGURES 
(Continued) 



Figure 



28. .Amounts of hourly use and plant damage 

for five survey days, Headsprings ■ 

Reach, Summer, 19 7 8 91 

29. Species damage in the Headsprings 

Reach, April to August, 1978 98 

30. Amounts of Sagitxaria torn and uprooted 
over varying levels of diving activity 

and amounts recovered in plots experimentally 
subjected to tearing and uprooting 10 3 

31. Size distribution of Sagittaria clumps 
uprooted, by divers compared to the size 
distribution of clumps sampled from the 

Devil's Eye Exclosure, which receives no use . . IC'-^ 

32. Damage Index for three reaches cf the 
Ichetucknee River 115 

33. Damage Index related to physical 
characteristics of the river and 

behavioral characteristics of use 117 

34. Fractional loss and fractional recovery 
rate cf Sagittaria , Myriophyllum , and 
Vallisneria ~ '. t ! '. T 121 



IX 



LIST OF COLOR PLATES 
Plate 

1. Headsprings Exclosure, July and 

November .,..,. 7q 

2. Tuber impact en the. Blue Hole 95 

3. Sagittaria bed, April and August, 13 7 3 97 

M-. Channel erosion in the Second Dock Area liu. 



Abstract of Thesis Presented to the Graduate Council 
of the University of Florida in Partial Fulfillment of the Requirements 

for the Degree of Master of Science 



CARRYING CAPACITY OF THE ICHETUCKNEE SPRINGS .AND RIVER 

By 

Charles DuToit 

June 1979 

Chairman: John Ewel 
Major Department: Botany 

A study was conducted in 1977-78 to determine the types and 
amounts of recreational use that the communities of Ichetucknee Springs 
and River can sustain without causing irreversible damage. I measured 
the kinds and amounts of damage which result from swimming, canoeing, 
diving and tubing, and monitored the recovery of aquatic communities. 
A carrying capacity, defined as the rate of use at which damage is 
equal to the natural ability of each plant community to recover, was 
recoiranended for each type of use. 

Tubing is, numerically, the most important form of recreation at 
the Ichetucknee Spri.ngs; 3000 people per day (the present limit) 
regularly float dowr. zhe River on tubes on summer weekends, and week- 
day use generally exceeds 1000. The reach between the Headsprings and 
the Slue Hole sustains the greatest impact, both in terms of channel 
and bank erosion and in terms of percentage loss of vegetation. Tram- 
pled plant beds support less shrimp and crayfish than healthy beds, 
and disturbed areas contain fewer types and numbers of fish than un- 
disturbed areas. The middle and lower reaches lose proportionallv less 
vegetation and, with some local exceptions, are not eroded bv recre- 



Xl 



ational use. Channel width and depth do not directly account for these 
differences, but changes in the behavior of users, who become more 
passive as they progress downstream, may be the most important factor. 
A limit of 100 tubers per hour is recommended. 

In winter, diving groups (2 to > 50 individuals) visit rhe Park 
to snorkel in the River and dive in the Blue Hole. Plant damage in- 
creases exponentially as diving activity in the Blue Hole increases. 
Crowding in the pool, poor group control, and trampling along the edge 
of the Slue Hole run account for this accelerated impact. The Sagit - 
t^aria community, which comprises 75% of the total cover in the Blue 
Hole, sustains the greatest damage. Recolonization of disturbed areas 
by Sagittaria is vexy slow in winter; the amount of regrowth in a day 
is about equal to the amount of damage caused by 50 divers in four 
hours. On busy days, when as many as 100 divers visit the Park, dam- 
age may exceed recovery by an order of ma,gnitude. To save the natural 
ecosystems in Blue Hole, a limit of 12 divers per hour should be en- 
forced. 

Swimming and canoeing are miner components of recrearionai use az 
the Park. Although swimming, and the trampling that accompanies it, 
result in loss of cover and bottom erosion, this activity is largely 
confined to the Blue Hole and Headsprings pool. Canoeing appears to 
have little impact on submerged plant comjnunities ; paddles cause little 
stem and leaf breakage and practically no uprooting. If the amounr of 
swimiaing and canoeing does not increase substantially, no limit need be 
placed on these i'.ctivities. 









Xll 



•' l^V,"' • 



INTRODUCTION 

The Ichetucknee Springs State Park, located in norrh- 
central Florida, is one of the State's most unique resources 
a clear, spring-fed river which winds through hammock, open 
marsh; and flocdplain forest. The Park, comprising an area 
of 910 hectares (2,250 acres), straddles southeast Columbia 
County and southwest Suwanee County, the Ichetucknee River 
forms a natural boundary between the rwc counties. The 
land for the Park was purchased in 19 70 by the State of 
Florida from a British mining firm, the Lcncala Pho3T:haTe 
Company . 

Geology 
The Ichetucknee Springs State Park (Fig, 1) lies in the 
v-oasta-L Lowla.nds , a physiographic region defined by surface 
elevations less than 30 meters (100 feet) above mean sea 
level and locally characterised by karst Tropograohy, evi- 
dent in the numerous springs, sinkholes, and limestone out- 
crops in the area. A geologic section in the area of tbe 
Park would show a surface mantle of sand and clay overlying 
a thick bed of limestone, about 915 meters (300 feet) deeo , 
which rests unconfoi-mably over Paleozoic basem.en- rock. The 
upper layers of limestone sec'iment , of lare Eocene a-e, are 
collectively called the Ocal.Jr group, v.hich, being highly 



ICHETUCKNEE Si=RINGS 
STATE PARK 

1.6 KIUOMETERS 



N 

i 




1/2 I MILE 

-"=>-=■ ROADS ^ S. ROUTE Q STATE ROUTE 
\» POWER LINE CUT PARK BOUNDARY 

PATHS 

PUNT COMMUNiTY KEY 

^ SANDHILL 
Q] HAMMOCK 
g MARSH 
^ SWAMP FORE 
^ PINE PLANTAT 



i: igure _ . 



Map ox Icherucknee Springs State Park. 
Map was prepared frcin aerial orotc^Tevhs 
(U.S.B.A., 3-31-7'+) and U.S.g'.S. "copo- 
graphic quadrangle (Hildreth, n, 1563). 



permeable , fcrms the dominant water-bearing formation in 
north-central Florida. This aquifer is overlain by Miocene 
deposits, the Hawthorn and Alachua formations, which con- 
sist of clay, phosphatic sand, and discontinuous beds of 
limestone. A surface depcsir, predominantly consisting of 
unconsolidated sand, was laid down over Miocene seaiment 
during rhe interglacial periods of the Pleistocene when sea 
level ranged 7.5-30 meters (25-100 feet) higher than ax 
present (Meyer 1962). 

The major geologic features of rhe Coastal Lowlands 
can be observed at the Ichetucknee Springs State Park. 
Ocala limestone outcrops in bluffs along the river; Miocene 
deposits containing phosphatic ore are exposed in mining 
pits in the hammC'Ck; and Pleistocene sands are everywhere 
evident in the Sandhill community at higher Park elevations. 

Hydrology 
The Ichetucknee River lies in an ancient basin, the 
Icherucknee Trace, which is roughly defined by the 50 foot 
contour level on U.S.G.S, topographic maps of south 
Columbia County. Rose Creek and Clay Hole Creek, in the 
vicinity of Lake City, form the headwaters of the basin. 
Surface flovj from these creeks is interceoted by sinkholes 
near the town of Columbia which is located about 16 kilo- 
meters (IG miles) southwest of Lake City. Here, the cao- 
tured surface flow mingles with groundwater and eventually 
emerges at the Ichetucknee SorinFS . 



Geologists believe that the Ichetucknee Trace developed 
along fracture lines associated wixh the uplift of the 
Peaainsular and/or Ocala arch (Meyer 1962). 

Ocala limestone outcrops, or lies at or just below the 
surf ace 5 in the Ichetucknee Trace. Ground water is dis- 
charged in areas such as the Ichetucknee Springs where the 
piezometric surface, or hydraulic head of the aquifer, is 
higher than the topographic surface. Geologists recognize 
two sources of discharge in the Ichetucknee Springs: 
1. ground water from regions of higher artesian head in 
northern Columbia County and surrounding areas , and 2 . 
local rainfall which enters the aquifer through sinkholes, 
limestone outcrops, or permeable sand deposits (Meyer 1962). 

The discharge of the major springs of the Park is shown 
in Figure 1. The average discharge cf the Ichetucknee River, 
measured at the Highway 27 Bridge, is 10,1 m^^/sec. (353 
c.f.s.), which ranks sixth in magnitude among Florida springs 
The minimum discharge recorded over a period extending from 
1917 to 19 72 was 6.8 m^/sec. (24-1 c.f.s.;, which is 33-= 







below average discharge. The maximum discharge during this 
period was 16.'+ m /sec. (5 78 c.f.s.), 51% above the average 
flow (Rosenau and Faulkner 19 7 4) . 

In Columbia County, groundwater rise generally lags 
five months behind the period of m.aximum rainfall, which 
occurs during rhe summer months (Meyer 1962). Small dis- 
charge increases, of shorr duration, result from local 

\ 
recharge by rainstorms. \ 



Water Quality 
The water temperature of the Ichetucknee River remains, 
year round, about 2 2'^C, which is approximately equal xo the 
mean annual air temperature of the region. Table 1 shows 
the chemical characteristics of the water from a 1945 
analysis (Ferguson et al . 194-7), Inspection of this figure 
shows that the river xvzater is alkaline (pH 7.7) and thax 
calcium and bicarbonate are the -wo most importanr dissolved 
mineral ions. Color was measured to be 0, indicative of the 
remarkable clarity of the spring water. 

Morphology of the Ichetucknee River 
Three reaches can be distinguished in rhe Ichetucknee 
River. The Headsprings, or Ichetucknee Springs, with a 
discharge of 1.3 m /sec. (45 c.f.s.), is the source of the 
"Headsprings Run," defined as that portion of the river 
between the Headsprings and the Blue Hole (Fig. 1), This 
reach is relatively narrow and shallow, with an average 
width of about 10 meters and depxh of 1 meter, and is par- 
tially shaded by hammock vegetaxion growing on the banks . 

The section of the river between the Blue Hole and 
Mill Springs, about 1,6 kilometers (1 mile) in length, is 
called the "Rice Marsh." Discharge from, the Jug Springs at 
Blue Hole (about 2.u m'^/sec). Mission Springs (1.^ m"/sec.), 
and Devil's Eye Spring considerably strengthens the river 

The "Headsprings Reach," a term used throughout this 
repcrt, includes the "Headsprings Run" and'^the 
Headsprings and Blue Hole. 









_ . — ^ 

6 


Table 1. Water quality of 


the 


Ichetucinee Springs. Data 


are from Ferguson 


et 


al. (1947). 




CHEMICAL 


ANALYSIS 




IJiarj 


17 


, 1946 








Pa 


rts Per Million 


Silica (3102) 






9.1 


Iron (Fe) 






.03 


Galci-un ( ca ) 






58 


Magnesium (Mg) 






6.6 


Sodi-Jin ( Na ) 






3.1 


Potassiiim (K; 






^ 

0. ;; 


Bicarbonate (HCO-,) 






200 


Sulfate (SO.) 






8.4 


Chloride (Cl) 






3.6 


Fluoride (F) 






^ 


Nitrate (NO^) 






1.0 


Dissolved- Solids^ 






188 


Total Hardness as CaCO_ 






172 


Car"06n Dioxide ( CCp ) 






6 


Other 


Measurements 




Color 






--t)^ 


PH 






7.7 


Specific Conductance ' K;clQ 


at 


25°G) 


32.9 


a. In a 1972-7.3 analysis by U.S. 
measured 170 mg/1 ( Rosenau anc 


•Ceological S\irvey 
L Faulloier 1974). 


dissolved solids 


b. Cclcr units are not specified 
IS based on a graduated scale 
to indicate the relative clari 
measures 200 or more on the co 


^oy 
of 

ty 

lor 


Fergiason et al. Their meas-orement 
colored disks and is presented here 
cf the water. Some swamp v/ater 
ed disk scale. 



flow in this reach. A short distance below Blue Hole the 
river widens to about 6 meters with an extensive marsh of 
wild rice, Zisania aquatica , bordering an open channel, which 
is 15 to 2 meters wide and about 2 to 3 meters deep. 

The "Floodplain Reach" is that portion of the river 
between Mill Springs and xhe point of discharge of the 
Ichetucknee River into the Santa Fe River. In this reach 
the river is 15 to 2 meters wide and 1-2 meters deep and 
is bordered by floodplain forest and limeszcne bluffs. 

Vegetation 
Three life forms of vascular plants are common in zhe 
open channel and floodplain of the Ichetucknee River: 
submerged macrophytes in the open channel, emergent macro- 
phytes in rhe marsh, and arboreal vegetation in the flood- 
plain swamp. Table 2 shows the comjnon species of rhe river 
and the upland communities. Sandhill vegetation occupies 
about 273 hectares (575 acres), or 30% of the Park area, and 
grows on Pleistocene sand deposits at higher elevations of 
the Park. Hammock trees grow in the rich calcareous soil of 
river banks and cover about 590 hectares (1460 acres), or 
6 5% of the total area. River plants and floodplain forest 
occupy about 5% of the Park. 

Natural History 
The Indian word ''Ichetucknee'' means "beaver oond." 
Ironically, beaver are rarely observed in the Park, and in 
fact, had not been seen for decades until the fall of 13 77 



Table 2. Coirmon species of the plant communities of the 
Ichetucknee Springs State Park. 



Sandhill 



Pinus palustris 
Quercus laevis 
Quercus margaretta 
Aristida striata 



longleaf pine 
turkey oak 
sand-post oak 
wire grass 



Mesic Hammock 



Quercus •'/irginiana 
Quercus hemisphaerica 
Magnolia grandi flora 
Carya glabra 
Persea borbonia 
Ilex oTDaca 



Acer barbatum 



live oak 
laurel oak 
southern magnolia 
pignut hickory 
redbay 

araerican holly 
florida maple 



Swamp Fcresi 



Taxodium distichum 



Nyssa biflora 
Nyssa aquatica 
Acer rubr^iom 



bald-cypress 
blackgum 
water tupelo 
red maple 



Aquatic 



Sagittaria kurziana 
Vallisneria americana 



Zizania aquatica 
Char a stT. 

I\/^iophyll^ja heterophyllum 
Ceratophyllijm decersiim 
Ludwigia rapenF 
Nasturxium officinale 
Na.jas guadalupensis 
Cicuta aaculata 
Pistia stratoites 
Fontinalis sv. 



eel-grass 

tapegrass 

wild rice 

musk-grass 

foxtail 

coontail 

red lud-wigia 

watercress 

southern naiad 

water-hemlock 

water-lettuce 

water-moss 



when one was observed in the Headsprings Run during the 
early days of our research. The long absence and recent 
return of the beaver is only one of the interesting features 
of the natural history of the Ichetucknee Springs. A monkey 
has been reported; wild turkey, bobcat, and deer are common- 
ly seen in the woodlands , and a great variety of birds and 
fish, as well as otter, inhabit the marshes and river. 

Less conspicuous features of the Springs are Eocene 
fossils of mollusks , echincderms , and foraminif era that are 
embedded in submerged limestone banks and emergenr bluffs. 
The bones of terrestrial vertebrates of the Pleistocene 
have been found in alluvial deposits along rhe Icherucknee 
River. The remains of an extinct bison were unearthed 
during the construction of a canoe ramp in 1373, and the 
bones of mammoths, mastodons, and a Pleistocene lion, Felix 
atrox, have been recovered at the Park. 

Cultural History 
Anthropologists believe that the Utina Indians, a tribe 
of the Western Timucuans , lived in the area of the Pax'k in 
prehistoric rimes. In 1950, John Goggin of The Florida 
State Museum, excavating a refuse mound, unearthed evidence 
ox a Spanish-Indian contact on the banks of Ichetucknee 
River. The recovery of both European and Indian artifacts, 
including a lead cross and ceramic vessels, suggested that 
a Spanish church formerly occupied this site, now known as 
Mission Springs (.Deagan 1972). The remains cf a -:rist mill 



10 

and earthworks at Mill Springs indicates more recent 
occupation of the riverbanks . 

History of Recreational 'Jse 
The type and amounts of use of the Ichetucknee River 
and woodland has changed considerably from pre-Park days to 
the present. Ferguson et al . , in a 1947 publication, The 
Springs of Florida , relate that the Headsprings was used 
for watering stock, as well as for swimming and picnicking. 
Fishermen and hunters frequented the river and uplands and 
camped on the wooded river banks. The river was additional- 
ly subject to unregulated use by local residents and college 
students, whose beer cans were conspicuously evident prior 
to a cleanup by the State. Under the administration of the 
Department of Natural Resources, the Park has instituted a 
number of regulations designed to limit environmental abuse, 
and has developed facilities to increase access and visitor 
comfort. A user now pays a 25 t admission charge; parking 
for cars and buses is provided at the Headsprings area, and 
trails and docks provide easy access to the river. Cainping 
is prohibited, and visitors are not allowed to carry food 
or beverages on the Ichetucknee River. A shuttle bus, 
operating from the Vvayside Park on Highway 27, transports 
users back to the Headsprings area at the end of a run. 

The Ichetucknee Springs under State ownership has 
become an extremely popular resource- its facilities, clean- 
liness, and recreational opportunities appeal to fair^ily 



groups, community organizations, tourists, dive clubs, and 
the general public. As shown in Figure 2, the amount of 
Park use has increased considerably during this decade. The 
amount of annual use remained fairly constant until 1976, 
when there was a 35% increase (about 50,OOC users) over the 
previous year's attendance. On July ^^ , 1S77, nearly 5000 
tickets were sold at the main gate. This was the largest 
amount of daily use ever recorded. 

Profile of Park Users 

In 197M- and 1975 a survey was conducted by the Florida 
Department of Natural Resources at the Ichetucknee Springs 
State Park to investigate the impact of crowding on a user's 
enjoyment of the experience. In addition to providing infor- 
mation on its primary objective, the survey furnished a 
sociological sketch of Park users. 

Male visitors outnumber female visitors by a factor of 
two or more. Approximately ''aS% of the Park users are 
between the ages of 19 and 26; 10% are under 18, and about 
25% betvieen 26 and 35. The city of Gainesville, which has 
grown rapidly during this decade, is xhe largest single 
source of users (35% of total), followed by Jacksonville 
Cabout 20%), and the Fort White area (about 10%). An inter- 
esring survey statistic shows that, on the average, rhere 
are nearly nine individuals per tubing party. This fact is 
likely accounted for by the large family groups, college 
fraternities, and communit37 organizaxions which regularly 
visit the Park, 



300- 



ANNUAL ATTENDANCE 



en 

or 

UJ 



250- 



CO 

■o 

c 

i 200- 
o 

x: 



U. 

o 

LiJ 
03 



50- 



00- 



50- 







1973-74 ' 1974-75 ' 1975- 76' 1976-77 ' 1977-78 ' 

YEAR 



Figure 2. Annual park attendance, 1973-7U tc 

1977-78. Data are from annual attendance 
records which are based on monthly use 
totals from July through the following 
June . 



13 

The Carryirig Capacity Concept 

The signs of environmental deterioration that have 

accompanied increased use of the Park in recent years have 

prompted the Department of Natural Resources to impose a 

limit of 3000 users per day, as well as to sponsor research 

on the "carrying capacity" of the Ichetucknee Springs and 

River. The concept of a recreational carrying capacity has 

become increasingly popular with resource managers; however, 

it is not always clearly defined, and has been difficult to 

apply. Lime and Stanky (1971, p. 175), in a review of the 

development of the concept, provide a good definition: 

The recreational carrying capacity is the 
character of use that can be supported over a 
specified time by an area developed at a certain 
level without causing excessive damage to either 
the physical environment or the experience of 
the visitor. 

In their definition, the authors emphasize the need for a 
multi-dimensional concept which includes three basic consid- 
erations: 1. user satisfaction, 2. environmental impact, 
and 3. the objectives of resource managers. The theoretical 
sources and applications of research in each of these three 
areas is summarized in the following discussion. 

User S'atisfaction 

The most comprehensive study to date on user satisfac- 
tion is the nation-wide survey conducted by the Outdoor 
Recrearion Resources Review Commission CORRRC 186 2) on the 
preferences and perceptions of users of Srate and National 
Parks . A n^jmber of other studies on visitor attitudes hav'e 



lu 

been conducted on a regional or local scale, such as the 
study by Lucas (196 3) on the perception of "wilderness" by 
different types of users of the Boundary Water Canoe Area in 
northeast Minnesota, and locally, the survey conducted at 
the Ichetucknee Springs State Park in 197M--75. Briefly sum- 
marized, the resulrs from these surveys demonstrate that 
Park users vary greatly in their recreational preferences, in 
their perception of environmental quality, and in their 
tolerance ro interaction with other recreationists . 

The recreational carrying capacity, from the viewpoint 
of user satisfaction y, has been defined as "the maximum num- 
ber of use-units (people, vehicles, etc.) that can utilize 
the available recreational space at one time for som.e 
activity while providing a 'satisfactory' experience for the 
user" (Lime and Stanky 1971, p. 174). The most popular 
application of this definition is the "space standard," a 
concept developed by the U.S. Forest Service which defines 
the amount of topographic space that a wilderness user 
needs in order to have a satisfactory day of recreation. 
The "space standard" for wilderness areas of National 
Forests is 3 acres per person per day (Douglas 1975). 

The assumptions implicit in the concept of a "space 
standard" are similar to those inherent in the theorv of 
the carrying capacity of natural populations. According to 
this theory, introduced by Verhulst in the 18th century, 
and mathematically formalized by Lctka, there is a limit 



15 



to the growth of natural populations due to density depen- 
dent interactions and shortages of available resources 
(Krebs 1972).. The concept of a carrying capacity for user 
satisfaction is analogous to the concept of a growth limit 
on natural populations in the sense that a "'space standard" 
ideally defines a level of use that an area can sustain 
above which density-dependent interactions (user-user 
contact) or environmental deterioration (recreational con- 
sumption of the resource) strongly detract from the enjoy- 
ment of the recreational experience. Although a "space 
standard" based on user satisfaction is a useful concept, 
it has a fundamental weakness. Lime and Stanky comment: 
"space standards based on user satisfaction have generally 
failed to incorporate the level of use the physical environ- 
ment can tolerate over a given time before serious damage 
results" (Lime and Stanky 1971, p. 175). 

Recreational Impact on the Resource 

The majority of research on impact of recreational use 
on natural ecosystems has been concerned with the effect of 
hikers , campers , and picnickers on the vegetation and soils 
of State and National Parks. Investigations of recreational 
impact on lakes and rivers have been primarily limited to 
studies on the environmental effect of outboard m.ctor dis- 
charge and watershed pollution (Stanky and Lime 1973). 
Basically, two approaches are used in research on recreational 
impact. One approach involves monitoring use levels and 



• 16 

measuring environmental damage in actual recreational 
situations. The other measures environmental damage under 
controlled levels of simulated impact, such as Wagar's 
(1964) use of a tamp to simulate trampling on foot paths. 
Recreational studies may be short term, such as Burden and 
Randerson's (1972) study on the effect of seven days of 
recreational use on a newly developed trail, or long term, 
as exemplified by Lapage ' s (1967) three-year study on plant 
cover changes at a New Hampshire campground. Historical 
investigations, such as Gibbens and Heady 's (196U) work at 
Yosemite , use time-series photographs, naturalist writings, 
survey reports, and interviews to determine environmental 
change over extended periods of time. 

The results of recreational impact studies have been 
used by the U.S. Forest Service to formulate a Ground Cover 
Index, which equates ground cover at a campsite with: 
1. the amount of recreational use in the area, and 2. site 
characteristics, such as slope and depth of B horizon. 

A problem with recreational impact studies is the 
element of uncertainty about the level of damage that a 
resource can tolerate without causing irreversible deterio- 
ration of a site. The consideration of this problem in 
other fields of ecology has led to the development of such 
concepts as ecosystem stability, resistance, and resilience 
(Bishop et al . 1974). Simply stated, these concepts are 
concerned with: 1. the ability of an ecosystem to resist 



17 

perturbation, 2. the rate and direction of recovery follow- 
ing disturbance (resilience), and 3. the threshold limit, 
or carrying capacity, beyond which the system is unable re 
return to its original condition. 

Concepts of this nature underlie a great deal of carry- 
ing capacity research and are implicitly acknowledged, if 
not openly recognized, in many resource management decisions. 
Wagar C1964) , in his tamp experiments, found that the 
"resistance" of Terrestrial vegetation to trampling was 
partially a function of life form; grasses and woody vines 
are generally less vulnerable to trampling than dicotyledo- 
nous herbs. Resource managers commonly use a variety of 
techniques, such as paving heavily-used walkways and ferti- 
lizing and irrigating, to increase the "resistance" of a 
site CLime and Stanky 1971). In England, Schoefield (1S67) 
determined the "carrying capacity" of a dune walk to be 7 50 
users per season. Increasing the amount of use beyond this 
threshold limit resulted in soil exposure and dune erosion. 
Schoefield also considered the "resilience" of this dune 
system when he estimated that an eroded footpath would 
recover in four years if protected from further use. 

Objectives for the Management of Recreational Resources 

The management objectives for a recreational area 
should be ideally based on 1. user demands and preferences, 
2. park philosophy, and 3. the durability of the resource. 
The park manager's problem of balancing recreation with 



preservation is similar to that of fisheries or agricultural 

enterprises where overexploitation m.a.y deplete the resource. 

The concept of "optimum sustained yield" as a management 

objective for the fisheries and agricultural industries may 

be just as applicable to the managem.ent of recreational 

areas. The "sustained yield" concept is implicit in the 

following statement by the Outdoor Recreation Resources 

Review Commission (1952, p. 1) on the goal of maintaining 

"site quality" in recreational areas. 

site quality. . .the extent to which an area 
provides its intended amounts and kinds of 
recreation opportunities while being main- 
tained in a long term productive condition. 



OBJECTIVES 

The objective of this research was to determine the 
amount of environm.ental change that results from varying 
types and amounts of recreational use. Information of this 
nature should greatly aid Park management in defining a 
carrying capacity that is consistent with their objectives 
of preserving the resource and meeting the public demand for 
recreation. To fulfill the stated goal of this research, 
answers to the following questions are provided. 

1. What is the relationship of plant damage to: 
--the nuuTiber of users? 

— the type of use? 

— the distribution of use, both daily and 
seasonally? 

2. What areas of the spring system and river, and 
which plant communities , are most disturbed by 
recreational use? 

3. What is the rate and kind of vegetation 
recovery following disturbance? 

4. What impact dees recreational use have on the 
animals of the springs and river? 

5. Is the damage to plant and animal comm^unities 
reversible or irreversible? 



19 



METHODS 



Base Mar) 



The Ichetucknee River was mapped ro determine the 
distribution of aquatic macrophytes , The method of mapping 
varied over the river, depending on the width and depth of 
the major reaches. The Headsprings Run, about 500 meters in 
length, was mapped in 10-meter sections using two fiberglass 
meter tapes and a meterstick. One meter tape was stretched 
across the run, perpendicular to the main channel. A seccna 
tape was stretched parallel to the first, 10 meters down- 
stream. The plant beds in each section were mapped by a 
wading observer who used the tapes ro chart bed position and 
the meterstick to measure the dimensions of the bed. Deoth 
was also measured in each section and rhs type of bottom 
sediment noted. The Blue Hole pool and run were mapped in 
a similar fashion, except the tapes were 5 rather than 10 
meters aoart . 

The portion of the river extending from the Blue Hole 
outlet to the wayside Park Landing was mapped using a boat, 
as the channel was too deep to wade. A 20-meter anchor 
rope, m.arkad at 5-meter intervals, served as a position 
reference by which an underwater observer charted the major 
plant beds. An assistant working from the boat rook dec-i-h 



20 

























21 




soundings 


, measured 


river 


wi 


dth 


with 


extension 


pel 


es. 


and 




recorded 


the compass 


dire 


cti 


on o 


- 


the 


main 


channel 


in 


each 




2 0-meter 


section. 

























Standing Croo 
Samples of each of the major plant species wei"'e clipped 
or uprooted from, quadrats of varying sizes. The samples 
were returned to the lab, oven dried (three days at 70^C), 
and weighed. The standing crop for each species was esti- 

mated by multiplying its sample weight/m" by its cover value 

2 
(m ), which was measured by planimetry of the base map. 

Plant Damage Survey 
The one-way flow of a river provides a researcher with 
an opportunity to directly measure the impact of tramuling 
on aquatic vegetation. The relaxionship of plant damage ro 
the amount of use can be estimated by counting users and 
collecting river drift simultaneously. This method was used 
throughout the study to measure the amount of damage to 
river plants over varying types and levels of recreational 
use . 

Winter Survey 

The impact of winter recreation was measured by sampling 
plant dam.age both on busy weekends and quiet winter weekdays 
over a period extending from December, 197 7, to March, 19 78. 
On sampling days, the researcher and his assistant collected 



drift for a four-hour period from a point in the river 
located just below the Blue Hole outlex (Station 1, Fig. 3). 
Handnets were used to retrieve plant clumps and fragments, 
and recreationists entering Blue Hole or passing the collec- 
tion station were counted and categorized according to type 
of use (scuba diver, snorkler, canoer, tuber, or swimmer). 
The netted material was returned to the lab, sorted accord- 
ing to species and type of damage (torn or uprooted) , oven 
dried (three days at 7 C) , and weighed. 

Summer Survey 



During the siomjner (April through August) , when recre- 
ationis-3 range over the entire springs system and river, 
plant damage was sampled one day each month from three 
different stations situated at the downstream end of each 
major reach. At Station 1, located just below Blue Hcle Run 
(same station used in winter survey), plant material was 
netted by two wading assistants, while a third counted and 
categorized users . At Stations 2 and 3 , located at Mill 
Springs and just below Wayside Park Landing respectively, 
drift was netted from either canoe or raft, as the depth of 
the channel prohibited wading. To assess the impact of rate 
of use (number of users per unit time), plant material was 
netted and the number of users recorded on an hourly basis 
throughout a sampling day. 

At the end of a survey day, all the collected plant 
material was rerurned to the lab, and, as was done in the 



23 



HEADSPRING REACH 



Ichetucknai Spring 

• C«dor Heod Spring 



FLOODPLAIN REACH 



Station 3 p-^^/"' 

)/ Tuber EjiI 





RICE MARSH 



Slue Hole Spring 

P Mitlion Spf inqt 

Devils Eye Soring 
SoqitlOfio 

Mill Spring 




Figure 3. Location of netting stations and 



experimental 



plots . 



The three netting 



stations are identified by number, the 
expei^imental plots by genus name. 



2 '4 



winter survey, sorted according to species and type of 
damage. As the available drying ovens could not accomniodate 
the large volume of vegetation, the sorted plants were 
spread on screens and drained for an hour before taking a 
fresh weight. Several small sam.ples (a handful) of each 
species were oven dried (three days at 70 °C) to determine 
a dry weight equivalent for the fresh weight measurements. 

Plant Resistance 
A simple experiment was devised to test the ability of 



a 



species to resist tearing or uprooting. One end of a 



nylon string was tied to a plant stem just above the soil 
surface. The other end was secured to a spring aligned with 
a meterstick. Resistance was measured as the maximum amount 
of spring stretch (in cm) at the point of tearing or 
uprooting. 

Changes in Plant Cover 
To dexermine seasonal changes in plant cover, three 
sections of the Headsprings Run (Fig. 4) were mapped in 
November-December, 1977, remapped in April, 19 78, and mapped 
again in August, 1978. The method was the same as was used 
in preparing the base map of the Headsprings Run: tapes, 
10 meters apart, were stretched across the run, and plant 
bed positions and dimensions charted on graph paper. 

Plant Recovery 
Several merhods were used to assess the rate of vege- 
tation recovery following disturbance. One method involved 



25 






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26 



monitoring the recovery of sample plots which were experi- 
mentally subjected to injuries similar to the kinds of 
damage (tearing, uprooting) caused by recreational use. A 
second method involved the measurement of plant regrowth in 
trampled beds , which were protected from further disturbance 
by fenced exclosures. A third way was to monitor plant 
growth in cages situated in areas of heavy recreational use. 

Experimental Plots 

Basically, two types of treatment were used to sim.ulate 
the types of injury which result from trampling: 1. Plant 
stems and leaves lying in the water column above a quadrat 
were cut back to the substrate level. 2. All rooted planxs 
lying within the boundaries of a staked quadrat were pulled 
from the substrate. Appendix A-4 describes the methods used 
to measure the regrowth of a number of plant species used in 
this experiment. 

Exclosures 

The Park staff constructed two fenced exclosures in the 
Headsprings Pvun (Pig. '4). One exclosure, situated between 
the Headsprings pool ourlet and the First Dock, protected 
an area that had been previously subjected to a moderate 
degree of trampling. A second exclosure was erected on the 
eastern side of the run opposite the Second Dock. Prior to 
fencing, the riverbed in this area had been extensively 
trampled by wading tubers. 



27 

Headsprings Exclosure . Vegetation recovery was moni- 
tored in two sections of the reach protected by the Head- 
springs Exclosure. At Site A (Fig. 4), a S-meter-long 
section of the run lying immediately above the downstream 
fence, the dominant plant beds were mapped on June 12, 1378, 
and on August 24, 1978. An open grid was laid out to provide 
a fixed reference for measurement of the beds . Nylon strings , 
marked at meter intervals , were stretched above the channel 
between pipes which were aligned in opposite pairs, one 
meter apart, along the banks. The position of plant beds 
was measured by running a plumb bob perpendicularly from the 
m^arked strings down to the submerged beds. 

A second section of the Exclosure, Site 3 (Fig. u.) was 
used to measure channel closure. A meter tape was strerched 
underwater from a pipe sunk in the channel floor to a second 
pipe sunk 10 meters downstream. Channel width was measured 
with a marked rod, which was held perpendicularly to the tape 
at each meter interval over this section. Measurements were 
taken on August 3, 1973, and October 12, 1978. 

Second Dock Exclosure . A heavily-trampled river bed, 
protected from further disturbance by the Second Dock 
Exclosure, was sectioned into eight 1 m units to facilitate 
detailed measurement of plant cover changes (Fig. U). In 
each unit, stakes vrere fitted tightly into the corners of 
a 1 m" quadrat and sunk permanently in the underlying 
substrate. Cover was measured on July 25, Septem.ber 6, and 



jau i»u jyjuffr 



28 



October 26, 1978, by positioning the quadrat, which was sub- 

2 
divided into one hundred 0.01 m units, over the stakes and 

mapping the areas occupied by the constituent species in 

each quadrat. 

In a separate section of the exclosure, the same method 

was used to monitor the recovery of Zizania plants in a 1 m^ 

quadrat (Fig. 4). In addition to mapping cover, plant size 

was noted by measuring the length of the three longest leaves 

of each Zizania plant in the quadrat. 

Cages 

Two cages were installed in the Blue Hole (Fig. 5). 
One cage, secured to the bottom in late May, was situated 
in the channel 10 meters downstream from the Jug, the spring 
water outlet in the Blue Hole. A second cage, installed in 
June, was situated about 5 meters from the Jug, on the souTh 
side of the Blue Hole pool. Both cages were made of hurri- 
cane fencing and had the same dimensions: 1 x 1 x 1.7 5 
meters . 

Run Cage . The cage in the channel, designated Run Cage, 
enclosed an area that was vegetated in part by Sagittaria , 
the remainder being open sand. On May 29, shortly after 
installation, the channel-ward edge of the Sagittaria bed' 
was marked with stakes to provide a reference for future 
measurement of vegetation outgrowth. Substrate level was 
measured on the stakes, which had been marked off at 
centimeter intervals. 



29 



^3Am 33N>IDni3H0l 




a) 
o 

rH 

•H 

W 
Q) 
bO 
fd 
O 

o 

c 
o 

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4-> 
(ti 
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in 
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30 



On July 6, about five weeks after installation, the 
bottom of the Run Cage was photographed to determine changes 
in plant cover. The substrate level was also measured to 
determine how much sediment was deposited during this period. 

At the end of the summer, the Sagittaria growth that 
had colonized the open sand area during the recovery period 
(May 2 9 to September 12) was mapped and then harvested 
(whole plants) to determine the net increment of Sagittaria 
cover and biomass in the Run Cage. Additionally, samples 
of Sagittaria leaf blades were clipped from two quadrats, 
one placed inside, the other outside the Run Cage. 

In the lab, the harvested Sagittaria plants were 
measured and oven dried (70°C) to constant weight. The 
leaves from the inside-outside samples were counted, measured, 
and then oven dried. 

Jug Cage . The cage situated on the south side of the 
Blue Hole Pool , called Jug Cage , covered a portion of a 
Sagittaria bed that had been subject to heavy disturbance 
prior to protection. On July 6, about a week after the cage 
was installed, leaf blades were clipped from quadrats placed 
inside and outside the cage. Two months later (September 
11) , two new quadrats were cut to determine changes in commu- 
nity structure (plant height and biomass) in both disturbed 
and caged sections of the Sagittaria bed. Leaves sampled in 
July were oven dried (70"C) to constant weighx. Leaves from 
the September samples were counted and measured prior to dry 
weight determination. 



31 



Response to Repeated Cutting 
Sagittaria kurziana, the most abundant plant in the 
Ichetucknee River, was used for an experiment on the effect 
of repeated disturbance on plant growth. Three replicate 
plots were used for each of three treatments applied to 
Sagittaria plants growing in a protected bed within the 
Devil's Eye Exclosure. All nine plots were subjected to the 

same kind of disturbance: the blades of all Sagittaria 

2 
plants rooted within a quadrat (0.12 5 m ) were cut back to 

the substrate level. The variable treatment factor was the 

number of times a set of plots was cut during a four-month 

interval extending from February 20 to June 13, 1978. One 

set was cut every two to three weeks, a second set was cut 

every four to six weeks, and the third was cut only ones, 

at the start of the experiment. On June 13, all nine sample 

plots, representing three treatments, were recut. The 

subsequent regrowth was harvested approximately five weeks 

later on July 21 and oven dried (70°C) to constant weight. 

Fauna Survey 

Invertebrates 



On August 5, 1978, a survey was conducted to determine 
the numbers and biomass of invertebrates inhabiting both 
disturbed and undisturbed plant beds. Figure ^ shows the 
location of three sampling sites in the headwaters area of 
the Headsprings Run. The first site, located inside the 
Headsprings Exclosure, had been protected from, tramolino- for 



32 

more than two months prior to sampling. The second site, 
in the Second Dock Exclosure, had been undisturbed for about 
three weeks prior to sampling. The third site, located just 
downstream from the Third Dock, was an area that had been 
subjected to trampling right up to the time of sampling. 

To minimize environmental variability, other than the 
degree of recreational disturbance, all sampling was done 
in Chara beds growing at shallow depths (less than 1 meter) 
along the edge of the channel. A stove pipe (diameter = 
15.8 cm) was used to extract two sample plugs of plant 
material at each of the three sites. The pipe, sharpened 
before use, was thrust down through a Chara bed into the 
sediment below. The sample plug, containing plants, animals 
and sediment, was lifted from the substrate with a flat- 
bottomed shovel and transferred to a fine-mesh net. The net 
was agitated in the water to remove fine silt and debris , 
then inverted into a plastic bag and returned to the lab. 

In the lab, the sample material was placed in white 
enamel pans, and all animals visible to the naked eye were 
picked out and sorted into species. The animals were pre- 
served in 5% Formalin, and the plant material was refriger- 
ated until the sorting of all sample m.aterial was complete. 
The plant material was then oven dried (70°C) to constant 
weight, and the animals drained and air dried (h hour) 
prior to counting and weighing. 



33 



Fish 

To assess the impact of recreational trampling on the 
fish populations of the Headsprings Run, a survey was con- 
ducted on August 10, 197 8, and October 13, 197 3, to deter- 
mine the types and numbers of fish in: 1. a disturbed area, 
the reach below the first dock; and 2. a protected area, the 
Headsprings Exclosure (Fig. M-). At each study site, a 20- 
meter rope was secured to an immovable object (dock piling 
or fence) and floated downstream. An observer, with face 
mask and underwater slate, slowly pulled him.self upstream 
along the rope, recording in his progress all fish seen 
along the run. Both the protected area and disturbed area 
were surveyed twice, in alternate runs, on each survey day. 
The presence of other conspicuous organisms, such as cray- 
fish or turtles, was also noted. 



RESULTS 

Base Map 

The Base Map (Appendix E) shows the plant cover in each 
of the three reaches of the Ichetucknee River. Although 
an average of 2 5% of the channel in the Headsprings Run 
is vegerated, there is great variation in the amount of 
cover over the course of this reach. In areas subject to 
heavy recreational trampling and/or shading, plant cover may 
be as low as 1%, In open, less disturbed sections, cover 
values measured as high as 8 0%. Chara sp. and Sizania 
aquaxica are the dominant plants in the Headsprings Run, 
each comprising about 2 5% of the total plant cover in this 
reach. 

Aquatic plants cover approximately 4-0% of the bottom in 
the Blue Hole pool and run. Sagittaria kurziana. is the 
dominant species in this area, accounting for SQ% of the 
extant cover, Sagittaria is notably absent at Icherucknee 
Spring and comprises only 3% of the plant cover in the 
Headsprings Run. 

In the Rice Marsh, about 5 0% of the channel bottom is 
vegetated. Over small stretches of this reach, however, 
cover may vary from 2 5% to 3 0%. Sagittaria is rhe dominant 
plant in the Rice Marsh, accounting for 55% of the total 



34 



35 



plant cover. Zizania and Chara cover less area, each com- 
prising about 15% of total cover. The remaining vegetated 
areas are comprised of Myriophyllum and Vallisneria , each of 
which accounts for 5% of plant cover, and Ludwigia and 
Nasturtium , which form small patches along the edge of rhis 
deep reach. 

The average amount of plant cover in the Floodplain 
Reach, measured over 65 map sections, is 22%, which is simi- 
lar to the average for the Headsprings Reach, The varia- 
bility of cover in this lower reach is, however, much lass 
than that of the Headsprings Reach. In the Floodplain Reach, 
the lowest cover in one section is lM-% (lowest cover in the 
Headsprings Reach is 1%). The maximum amount of cover is 
32% (maximum, cover in the Headsprings Reach is 80%). 
Myriophyllum and Chara are the two most common plants of the 
Floodplain Reach, accounting for 37% and 30% of total cover, 
respectively. As the Base Map shows, Sagittaria (20% cover) 
and Vallisneria (10% cover) grow along the edge of the chan- 
nel in this reach. 

Types and Amounts of Recreational Use 
Figure 6 shows the types and amounts of monthly recre- 
ational use from January -August , 1978. It is evident that: 
1. weekend use is much greater than weekday use, usually by 
a factor of three or more and 2 . the num.ber of visitors 
increases substantially during the warm summer months. On 
the average, about 15 people visited the Springs on a 



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winter weekend day in January. By April, average weekend 
use had risen to nearly 10 visitors per day. By midsiajrjner , 
the number of weekend visitors consistently reached 30 00 per 
day, the present Park limit on recreational use. 

Figure 6B shows that divers constitute about 85% of the 
total number of winter users. Canoes account for about 10%, 
and swimmers and tubers comprise 5% of the total winter use. 

The onset of warm weather in April signals the start of 
the tubing season. The proportion of tubers jumped from 10% 
of total use in March to 60% in April, and conrinued to 
increase during the spring. By June tubers accounted for 
95% of total recreational use. This level of tubing activity 
was sustained throughout the summer months. 

Plant Damage Survey 

Winter Survey 

The relationship of winter plant damage to: 1. total 
number of users (includes all types of recreationists) and 
to 2. number of divers (includes only 3;cuba divers and 
snorklers) is shov;n in Figure 7. Examination of this figure 
shows that the relationship of damage to Total number of 
users is not consistent. This lack of relationship, in 
effect, is best explained by the observation that canoeists, 
who were included in the determination of total amounts of 
use, generally have very little impact on the submerged 
plant communities of the river, Underv/ater assistants on 



o 



5 

c 
a 
> 
o 



700-j 
600- 
500 
400 



uj 300- 
o 




20 



40 60 80 

DIVERS (no. /day ) 



100 



120 



Figure 7, Winter plant damage 27elated to total number of 

users and to number of divers. Relationship of 

plant damage (y) to number of divers (x) is 

described by the exponential equation, 

O.OUx , 2 
Cr 



y = 14 . ^e 



0.39) 



The notation "J. 7" indicates the data point 
for January 7 which is mentioned in the text 



39 

a number of occasions, watched canoes pass over plant beds. 
Although paddling stirs the surface of the beds, it results 
in very little stem or leaf breakage , and practically no 
uprooting. On days when canoeists constitute a large pro- 
portion of total use, as occurred on January 7 (66 canoeists, 
24 divers, 15 tubers, and U swimmers) plant damage was expec- 
tedly very light. 

The relationship of damage to number of divers (Fig. 
7), shows that plant damage predictably increases as winter 
diving activity increases. As the number of divers increases, 
the amount of tearing and uprooting increases exponentially. 
Less than 5 dry grams of plant material was netted on days 
when less than M-0 divers were counted. On busier sampling 
days, when the number of divers ranged from 60 to 100, the 
weight of the netted material ranged from 200 to 500 dry 
grams , a disproportionate increase relative to the amount 
of use . 

Species damage . Figure 8 shows the amounts of species 
damage over varying levels of diving activity. One species, 
Sagittaria kurziana , accounted for 40% of the total weight 
of plant material collected during the winter survey. The 
relationship of Sagittaria damage to the n'am.ber of divers is 
similar to that of total plant damage and divers in that 
impact accelerates when more than SO divers use the resource. 
Damage to the other species is less predictable over varying 
levels of diving activity. When the amounts of damage to 



^Q 



aoc 

600- 
400 
200 

500i 



-r 400 



300-1 



UJ 

o 
< 
Z 
< 

Q 



200 



100- 



WINTER 1977-78 
Sogittoria nurzicna 




• Total damagul"-) 

o Torn ( — ) 

^ Uprooied i ) 

8 



/ /o 



' •/ 



/ / 




20 



40 60 80 

DIVERS (no./day) 



Figure 8 . Damage by soecies , related to number of divers , 
Winter, 1977-73. For Sagittaria kur::iana , the 
relationship of damage (y) to number of divers 
(x) is described by an exponential equation: 

number of clumps uprooted, y = 50. 7e ' (r"=0.83); 

torn fragments, y = i.5e°-°^^ (r^=0.7a); uprooted 



clumps, y 



2.7e0-^^^'^ (r2: 



:0.86) 



41 



SPECIES DAMAGE-WINTER 




30 40 50 60 

DIVERS (no./day) 



120 



100 



o 
■o 



80 



>> 

w 
T3 
C 
O 



o 
< 

< 
a 



60 



40 



20 



Cerolophvilurn <3am»fsum 



■ NQSfuflium of ficinole 

* - - ~ Myriopflylluffl heferopliyllum 




lO 20 30 40 50 60 

DIVERS(no./aay) 



70 ao 



Figure 3. Damage by species, related ro nur.iber of 
divers, Winter, 1377-73 (continued). 



42 



these species is considered collectively, however, it is 
again evident that when the nximber of divers exceeds 60, 
there is a marked increase in the amount of tearing and 
uprooting of river plants . 

Figure 9 shows , for each species , the percentage of 
total damage and the percentage of total standing crop. It 
is important to note that both damage and standing crop 
values are estimates. The amount of plant drift netted is 
undoubtedly less than the amount of plant material actually 
torn or uprooted- and standing crop estimates are based on 
a limited number of samples . The figure suggests that for 
most species the amount of damage is proportional to 
standing crop . 

Chara appears to be an outstanding exception to this 
assumption, in that the small amount netted is not propor- 
tional to its large standing crop. This disproportion is 
likely due to the difficulty of collecting this species. 
Unlike other plants, Chara rolls on the bottom of the 
channel, making it especially difficult to spot and retrieve 
on busy days when the water turns nearly opaque with sus- 
pended sediment. 

Ludwigia and >Ty r i o phy 11 urn also appear to be exceptions 
to the assumption that damage is proportional to standing 
crop. As both Ludwigia and Myriophyllu m could be netted 
fairly efficiently, it appears that they may be selectively 
damaged. Ludwigia accounted for 15% of the tctal weight of 



43 



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44 

plant material netted during the winter damage survey. 
However, the standing crop of Ludwigia comprises less than 
1% of the total standing crop of the Headsprings Run and 
Blue Hole area. Myriophyllum comprised 7% of the total 
damage, but like Ludwigia , accounts for about 1% of the 
total standing crop. 

Although Sagittaria accounted for 4 0% of the total 
damage, it also accounted for 3 5% of the total standing crop. 

Summer Survey 

Figure 10 shows the relationship of plant damage to the 
amount of daily recreational use in the three reaches of the 
Ichetucknee River. The largest amounts of drift were netted 
from the Rice Marsh reach. Similar amounts of vegetation, 
about 20 00 dry grams, or 4 5 lbs. fresh weight, were netted 
on May 21 and June 14, when 1500 and 500 people, respectively, 
were counted. On July 9 and August 5, when 2200 and 2700 
users were counted, the amounts of damage more than doubled; 
about 4500 dry grams, or 100 lbs. fresh weight, was collected 
on each of these days. 

The amount of drift netted from the Floodplain Reach 
was much less than the amounts netted from the Rice Marsh. 
On June 14, 810 users were counted and about 1000 grams 
netted. On May 21 and July 9, at use levels of 20 24 and 
2055, 2744 and 2322 grams of plants were netted. The plant 
drift collected on August 5, when over 3000 users were 






6000 



5000 



a 



4000 



•o 3000 

c 



o 2000 
< 

< 

o 

1000 







PLANT DAMAGE- SUMMER 



^Headsprings Reich ( ) 

O Rice Marsft ( 1 

• f loodplain Reech ( — ) 



^O 




J_ 



1000 



2000 
USERS (no./day) 



3000 



1000 



Figure 10. Amounts of daily plant damage and daily use in 
three reaches, Summer, 197 8. Relationship of 
damage (y) to users (x) for each reach is de- 
scribed by a linear equation: Headsprings 

Reach, y = 307.5 + 0.5 3x (r^ = 0.57); Rice 

Marsh, y = 1000.1 + 1.32x (r^ = 0.35); Floodplain 

Reach, y = 1250.0 + 0.43x (r'^ = 0.55). 



46 

counted in this reach, weighed 26 3 7 grams, an amount similar 
to that netted during the 2000-user days in May and July. 

The amounts of vegetation netted from the Headsprings 
Reach generally weighed less than the drift collected from 
the other two reaches. Figure 10 shows that in the 500 to 
1500 user range, plant damage consistently increased with 
use. However, the amount of drift netted on the two 30 00- 
user survey days varied greatly. On Sunday, July 9, 2851 
users were counted, and about 2400 grams collected. On 
Saturday, August 5, the amount of use (2864) was similar, 
yet the amount of drift collected, 1083 grams, was less than 
half the amount netted on July 9 . 

Figure 11 shows that, for all three reaches, the .amount 
of plant damage generally increased over increasing levels 
of hourly recreational activity. However, the variability 
of the results makes it difficult to predict rhe amount of 
damage for a specified level of use. Despite this variabil- 
ity, it is evident that over similar amounts of hourly/ use, 
plant damage in the Rice Marsh was greater than the damage 
in the Floodplain Reach or Headsprings Reach. 

Figure 12 is similar to Figure 10, but describes 
dam.age in each reach as a fraction of the total standing 
crop of thar reach. This figure clearly shows that recre- 
ational use generally removes a much larger fraction of the 
standing crop of the Headsprings Reach than it does in the 
middle and lower reaches. One notable excei^tion occurred 



47 



2000 r 



1500 






* 1200 

>« 

w 

e 



y 800 



< 



400 



• Headsprings Rsach 
Q Floodploin Reach 
O Rice Marsh Reocn 



a 



PLANT DAMAGE -SUMMER 
O 



a a 
a 

1 o 






250 



500 750 

USERS (no./hr.) 



1000 



1250 



Figure 11. Amounts of hourly plant damage and use in 
three reaches, Summer, 19 78. 



48 



2.o^ 



^ 1.5-j 
a 



q 1.0 



O 

P 0.5H 
o 

< 



• Heodsohngs Reoch 

O Rice Morsh 

A Floodplain Reach 






1000 



2000 3000 

USERS (no. /day) 



4000 



Figure 12. N'omber of users and fractional loss of 

standing crop, for three reaches, Summer, 
1978. 



Fractional loss = 

total damage /day (oven dry wt 



srarns ) 



standing crop Coven dry st . , grams ) 

The letter "a" indicates data points foi 
June 11+ which is mentioned in the text. 



^9 

on June 14, the only weekday sampled, when The carnage was 
low, and about the same, for all three reaches. 

Species damage . Figure 13 shows the percentage damage 
and percentage standing crop of each of the major species 
in the three reaches of the Ichetucknee River. 

In the Headsprings Reach, the amount of damage to a 
species was generally proportional to the size of itsr 
standing crop (see Sagittaria , Zizania , Myriophyllum , 
Ludwigia , and Nasturtium ) . A few species, however, sus- 
tained disproportionate amounts of damage. The percent 
Cicuta damage (22%) was twice as large as its percent 
standing crop (11%). In contrast, the percent Chara dam.age 
(8.1%) was less than half its percent standing crop (25%). 
As previously stated, the data for Chara reflect the diffi- 
culty of netting this species. 

For most Rice Marsh species, the amounts netted were 
generally proportional to their standing crops. Chara was, 
again, an exception (1% damage, 20% standing crop). 
Vallisneria was another, but the amount netted (2 5% total 
damage) was disproportionately large relative to its 
standing crop (5% standing crop). 

In the Floodplain Reach, percent total damage was 
similar to percent total standing crop for most species 
"^^^?^ Myriophyllum and Sagitiraria . Whereas Myriophyllum 
appears -o be selectively damaged (37% damage, 15% standing 
crop), Sagittaria appears to sustain relatively little 
im.pact in rhis reach (16% damage, 30% standing crop). 



50 



50 
40 



Uj 30- 
o 
or 
UJ 20 

Q. 



10- 



UJ 

o 

UJ 

Q- 




70 

60 

50-1 

40 

30- 

20 

lO-l 






I 



i 



HEADSPRINGS REACH 



I 



A 



-dCL 



I 



RICE MARSH H Percent of standing crop 

I I Percent of total netted in 
summer, 1978 



t^ I r-7 



h 



A 



LJZl 



50-) 
40 

5 50H 
o 

S 20 
Q. 

10 





V. 



'A 



FLOODPLAIN REACH 



i 



/, 



a 



^ 



Sagittaria Myriophyllum Valisnerio Nasturtium Ceratophyilum 

Zlzania Chora Ludwigia Cicuta 

SPECIES 



Figure 13. 



Percent total damage and percent of total standing 
crop (total weight of plants in each reach) for 
plant species in three reaches, Sunraier, 197 8. 



51 

Plant Resistance 

Figure 14 shows the average amount of spring force 
required to tear or uproot the stems of several aquatic 
species common to the Ichetucknee River. The large species, 
Zizania and Sagittaria , offered considerable resistance: IC 
and 6 poundaC+.B and 2.7 kg) of pull, respectively, were 
required to dislodge these plants. In contrast, the stems 
of Chara , Ludwigia , and N"asturtium tore under a light pull 
equivalent to about 0.3 pounds (0.1 kg) of spring force. 
Myriophyllum stems were moderately resistant, tearing at 
0.5 pound (0.2 kg) of pull. 

Figure 14- also shows a large variability among the in- 
dividual plants tested for each species. Resistance measure- 
ments on several different-sized plants showed that smaller 
arid/or shallow-rooted Zizania and Sagittaria plants pulled 
free from the substrate much more readily than plants which 
were buried under a layer of sediment. In fact, stem.s 
buried at depths greater than 10 centimeters could not be 
dislodged. Under increased pull the leaf clusters of deeply 
buried plants tore free at the soil surface, leaving the 
perennial stem.s intact below. 

Changes in Plant Cover 
Figure 15 shows the changes in plant cover in three 
sections of the Headsprings Run over two successive seasons 
(.winter and summer) of recreational use. It is evident that 
a substantial amount of vegetative regrowth occurred between 
Movem.ber-December, 1977, and April, 1978, and that over the 



52 



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MAP SECTION H 
11-18-77 













/ 



y 









53 



U-U-78 




9-21-78 



////// 






////// 



// / / / 






/:/,;/ 



•si 






KEY 
2] Ceratcphyll^Lm 



y/^^y//A 








M Mv-riorhvll-um 



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Hvdrocoxvl 



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I I Open 



areas 



Figure 1 



Seasonal changes in plant cover in three 
sections of the Headsprings Run. Section 
H, 5 meters in lenigth, is located iimedi- 
ately downstrean of the First Dock. 
Sections Q ar..d R, each 10 ineTers in lengrh. 
aire cc ntig^uous and are located opposite 
and iust below the Thiixi Dock. 



MAP SECTION Q 
12-12-77 




14-4-78 




9-21-78 




i:lg?jre 15. Continued. 



MAP SECTION R 
12-2-77 



55 




9-21-78 




Figijre 15. Continued. 



5 6 

following summer these same sections sustained a heavy loss ■ 
of plant cover. 

Map sections Q and R show the winter recovery and 
summer loss of Chara and Zizania cover in the Third Dock area 

Planimetric measurements showed that Chara cover in section 

2 
R increased about 12 m over the winter, but decreased about 

2 
b m over the rollowmg summer. Zizania cover, almost non- 
existent in section Q in December, 197 7, increased greatly 
in this area over the winter. However, this new growth was 
trampled back during summer 19 78 ro about the same level as 
was originally mapped the previous Novem.ber. 

Kydrocotyle and Ceratophyllum , two minor species com- 
ponents of the Headsprings Run, showed a large 'amount of 
growth in section H between November", 1977, and April, 1978. 
The increased coverage of these two species, as well as that 
of Zizania , resulted in a narrowing of the open channel 
floor from about k meters in November to about 2 meters in 
April. Nearly all of the Ceratophyllum winter growrh , as 
well as a considerable amount of Zizania , was trampled out 
the following summ.er, resulting in an enlargement of a 
channel width to about 3 meters by September, 197S. 

Experimental Plots 

Sagitxaria 

Two trends are apparent in Table 3- and Figures 15-18 , 
which show the results of the Sagittaria growth exceriment 



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800 



EXPERIMENTAL PLOTS 
Soqittofio kurziana 



600 



- 400 

>- 
a: 
uj 
> 
o 
o 

UJ 

a: 200 - 



< 

UJ 



O Lcof fttonding crop 

• Cut pioK 

▼ Tim« o1 cutting 




FeOruoiTT 



March 



April 



May June 

MONTH 



July 



August 



Figure 16. 



Standing crop and recovery of Sagittaria leaves 
following cutting. Bars show standard deviations 
of means based on three replicate ploxs (0.125 m2) 



o _ 

g~ !000 

2 =• 

Q -." 
2 « 

? £> 
in -o 



500 



UJ = 

o - 

o ^ 

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a. -a 

If 




300 



200 - 



100 



EXPERIMENTAL PLOTS 
Sogitfaria kurziana 



Februory I Morch ' 



April 



May 



June 



July 



' August ' 




jonuory ' Feoruory I 



▼ Time ot uprooting 






0' — T 

Februory' Morch 




i 



April 



Moy June 

MONTH 



July 



August 



Figure _7. Standing crop and seasonal recovery of Sagi ttaria 

clumps following uprooting. Bars (, 4 ) show 

standard deviations of means based on three 
replicate plots ('0.125 ro2). 



61 



lOOOn 



Februory 



O Sraridinq crap 
• uorooied plan 




Figure 13 



Number of Sagittaria clumps counred m 
quadrats following uprooting , and 
standing crop (no. of clumps) m 
undisturbed quadrats sampled m February 
and June, 197 8. 



52 



conducted at the Devil's Eye Exclosure: 1. The rate of 
regrowth following disturbance is much greater in summer 
than winter. 2. Plots in which only above-ground parts 
(leaf blades) were cut regrew more rapidly than plots in 
which all plant material (leaves, stems, and roots) was 
removed from the substrate. 

Winter growth . Inspection of Table 3 shows the 
differences in winter growth rates between cut plots and 
uprooted plots. On March 21, about one month after the 
initial disturbance (Feb. 20), the uprooted plots contained, 
on the average, about 1 gram of biomass/m"". Over the same 
period, the cut plots had produced about 13 grams of new 
leaves. On June 13, nearly four months after the plots were 
first disturbed, leaf material harvested from cut plots 

weighed about 300 grams /m" , while whole clumps, harvested 

2 
from uprooted plots, weighed about 200 grams/m . 

These results indicate that, following an initial lag 

period (Feb . -March) , clump production proceeded relatively 

rapidly, reducing the magnitude of biomass differences 

between the uprooted and cut plots . 

Summer growth . The growth of Sagittaria cliomps in 
uprooted plots is much more rapid in summer than winter. 
On July 28, ^0 days after three sample plots were initially 
uprooted (June 13), rhe mean weight of the new growth was 
about 35 grams/m." (Fig. 17), In contrast, plots uprooted 



53 

in February had produced less than half this amount after 
70 days of regrowth. Again, as in winter, there was a more 
rapid accumulation of biomass in cut plots than uprooted 
plots. Over the 40-day period mentioned above (June 13 - 

July 28), the cut plots (Fig. 16) produced about 110 grams/ 

2 
m of new leaf biomass, about three times the amount of 

o 

clump biomass (35 gvams/m") produced in the uprooted plots 
(Fig. 17) during the same period. 

Standing crop . Results from sampling in undisturbed 
plots show that the standing crop of Sagittaria is signifi- 
cantly greater in summer than winter. The oven dry weight 

of plants (including leaves, stem^s , and roots) sampled on 

2 
February 20 was 563.8 grams/m . Plants sam.pled on June 18 

weighed 1000.5 grams, nearly a 100% increase over the winter 

weight (.Fig. 17) . The biomass of summer leaf blade samples 

was also significantly greater than the biomass of winter 

leaf blade samples (Fig. 16). The mean weight of leaf 

blades sampled on February 2 was 439 grams/m ; the s'lmmer 

o 

biomass was 692 grams/m . 

Interestingly, the number of clumps in sample plots 
did not change seasonally (Fig. 18). On February 20, 

sampling showed an average of 101 clumps/m . On June 18, 

2 
the mean number of clumps was 10 6 /m , a nonsignificant 

increase. 



6U 



Myriophyllum, Chara, Zizania 

The pattern of Myriophyllum recovery was markedly 
different from that of Sagittaria . Myriophyllum. plots cut 
in February regrew at about the same rate as plots cut in 
June (Fig, 19). Also, the relative recovery of Myr iophyllum , 
expressed as the ratio of biomass recovered to standing 
crop, was greater than that of Sagittaria . Over a period 

extending from February 2 2 to March 23, Myricphyllum plots 

2 
(0.12 5 m ) in which all the above-ground material was 

clipped to the substrate level, recovered about 9 8 grams/m 

of stem and leaf material, almost 60% of the original amount 

2 
cut (about 170 grams/m ). In contrast, Sagittaria plots, 

clipped back to substrate level on February 20, had recovered 

only 13 grams/m"", or 3% of their original biomass (about "440 

2 
grams/m ) at the time of harvest on March 21, 

Chara , like Myriophyllum , recovered relatively rapidly 

following cutting (Table 3). Between February 20 and March 

25, Chara plots in the Floodplain Reach produced, on the 

average, 3 71 dry grams/m of new growth, almost 4 0% of the 

original -amount cut (961 dry grams/m ). Plots cut from a 

bed in the Headsprings Reach in summer did not exhibit as 

rapid a recovery as did the February plots at a downstream 

site. After a 2 7-day period (the recovery period for the 

February plots was 29 days), the Headsprings Reach plots 

contained, on the average, about 125 dry grams, which was 

only 20% of rheir original biomass (641 grams/m").' 



65 



EXPERIMENTAL PLOTS 
Myriophyllum hgtefoohyllum 



400 I- 



"w 300 



Roodplain Reach 

O standing crop 
• Cut plot 

Heodspring Reocij 
O Standing crop 
■ Cut plot 



>- 
(C 
Ui 

> 

o 
o 
llJ 

cr 



200 



100 - 




February ' March 



July- I August 



Figure 19 . Standing crops and regrowth of Myriophyllura 
following cutting. On February 22, March 
30, and May 5, two plots (0.12 5 m2) were 
- clipped from a bed in the Floodplain Reach 
and harvested after a "4-6 week recovery 
period. One plot (0.12 5 in2 ) was cut on 
June 12 from a bed in the Headsprings Run 
and harvested on July 25. Bars show 
standard deviations of sample means. 



66 

Table 3 shows the recovery of several other species 
following cutting. The pattern of recovery of Zizania 
aquatica exemplified the ambiguiry of results obtained from 
some of the test plots. In June, several Zizania plants in 
a quadrat in the Headsprings Exclosure were cut back to 
substrate level. A month later, none of the plants origi- 
nally cut could be found, and a thick felt-like layer of 
algae covered the sample area. The only macrcphyte observed 
in the quadrat was one Zizania clump, not one of those origi- 
nally cut , which appeared to have emerged from the substrate 
during the recovei'^y period. In contrast, several Zizania 
plants, cut back in the channel of the Floodplain Reach, 
recovered about 16 centimeters of leaf growth over a 5 -day 
period in February. 

Results from Vallisneria plots indicate that the 
recovery of this species may be dependent on the initial 
vigor of the bed. Plots which showed a relatively large 
standing crop prior to disturbance (cutting or uprooting) , 
exhibited much more regrowth (Table 3) than did plots having 
a low standing crop . ^^. 

Exclosures 



Headsprings Exclosure 

Figure 20 shows the change in channel profile and 
shifts in the positions of the dominant plant beds in a 
section (Site A) of the Headsprings Exclosure monitored over 



67 



HEADSPRINGS EXCLOSURE 

JUNE 12,1978 




AUGUST 24, 1978 




Z c~^ o° a^ a^ a^ n^ a^ n^ C'- '^ -I 













^^ 



Myriophyllum 



Ziianio -submerged 



-0°Q°0- 

o;;o-c-o"o2oxoo = °/ 

o=o2o^o=o; 
c2o2o5o5=35-ogo; 



°oSo-o^o; 



■* - o ^ ' 



. -°o=?=S 
ogo2o2o5o2oXo 



°o°°°c': 



w ^_. O ^ C ""A 

og5gS=S§S2o°o2SiS2S°§°. 
o2c2c2o2§2S5§252S2gsS9^v 



o05=s=iPPPispc§ 



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c;;o 



0^2 



cXoXo'o 



.J^Or 



•^ 00 Coco 

= 5§5§cg5°5p§c^5§So§oao§ 

Sg5gSxogS§o2Spg§o°ogcgo 
o.o,c2=§c2ogoOogo,oScg= 



°oSS5goCp?; 



o"o'^o'^o°a°o'^o 

°SSS252oSogg gggggggggggg 



METERS 



I 



/^ Ludwigia 
Chara 



"o<j Zizania- emergent 
1^ Shrubs 



^iBI.Gn. Algae 



Figure 2C. Change in plant cover, Site A 
E.xclosure, 6-12-73 to 8-2'4-78 



Headsprings 



■•T?r%"ii^n>ip^Bi»" ' ii ■ -r ji.ppi 



the summer of 19 78. Between June 12 and August 24, 19 78, 
channel closure averaged about 7 centimeters over the 
length of this 5-meter section. As the figure and time- 
series photographs show (Plate 1), the vegetative expansion 
of several species, including Char a , Myriophyllum , Ludwigia , 
and Zizania , resulted in a narrowing of the channel. 

Figure 21 shows the change in channel profile of a 
second exclosure section (Site 3), locaxed just upstream of 
the 5-meter map section. The average amount of closure, 
measured at one-meter intervals over this 10-meter section, 
was about 4 centimeters over a two-month period in summer. 
A notable feature, evident in both the IC and 5 meter sec- 
tions , is an increase in profile irregularity as natural 
forces become more important than human disturbance in 
shaping the growth patterns of submerged plant beds. 

Second Dock Exclosure 

The change in plant cover in eighx 1 m"^ quadra-cs, 
protected from recreational disturbance by the fenced exclo- 
sure opposite the Second Dock, is shown in Figure 22. 
Between July 24 and October 26, plant cover increased in 
four of the quadrats, but showed little change in the others. 

Quadrats 1, 3, and 6, which contained largely bare sand 
prior to exclosure, remained in essentially the same condi- 
-ion over the measurement period. Sm.all patches of blue- 
green algae shifted in position, but did not increase rhe 
plant cover in quadrars 1, 2, and 3. In fact, the only 



Plats 1. Headspr-ings Ilxclosure, July and November, 137 8. 
This section cf the channel, lying immediately 
above the downstream fence was photograpned from 
approximately the same position one month after 
the exclosure was erected (A) and four months later 
in November (B). Several changes are apparent: 
the growth of individual plant parches, the closing 
of the open channel , and the diversity and beauty 
of a protected reach. 



70 








CVlT 



(O 



2 



O-"- 



HEADSPRINGS EXCLOSURE 
Channel Profile 




8- 3-78 
10-12-78 



Centimeters 







50 



Figure 21. Change in channel profile, Site B, 

Headsprings Exclosure, 8-3-73 to lC-12-7i 




;ecohd dock excidsure 



7-25-78 



72 







3-B-73 








m 



Myriophyllum 
heterophyllum 

Algae (blue- 
green color) 



IMtlER 



^i; Algae (brcwn color) 



piij C har a and algae 
Zizania aquatica 



Figure 22. Change in plant cover, Second Dock 
Exclooure, 7-25-78 to 10-26-78. 



73 

evidence of new plant growth in 1, 3, and 6, was a Zizania 
seedling, which appeared in quadrat 1 at the time of the 
third mapping on October 26. Quadrat 2, tucked in a quiet 
shallow, appeared to be dominated by algal growth which 
showed a slight decrease in coverage during the study. 

The vegetative cover in quadrats 4, 5, 7, and 8 in- 
creased considerably between July and October. On June 25, 

2 
the date of the first mapping, Chara covered about 1.1 m of 

the bottom in this four-quadrat section; 4 3 days later, on 

2 
September 6, Chara cover measured 1.6 m , representing an 

2 
average rate of increase of 115 cm /day. 

2 2 

On October 26, Chara beds covered 2.0m of the U.O m 

9 

section, having grown at an average rate of 8 cm^/day 
since September 6. 

Myriophyllum cover did not change much over a three- 
month period. On July 25, Myriophyllum cover in quadrats 

2 
4, 5, 7, and 8 was 0.2 5 m ; on October 26, this species 

2 
covered 0.25 m , a negligible increase. 

Figure 2 3 shows that the number of Zizania plants in a 

fixed quadrat did not change between August 3 and September 

26, 1978. However, the size of the individual plants did 

increase. On August 3, the mean length of Zizania plants 

was 6 6 centimeters. On September 25, mean plant length was 

77 centimeters. 

2 
The change in plant cover observed in this 1 m quadrat 

was almost entirely due to the vegetative expansion of Chara. 



74 



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75 
Blue Hole Cages 

Jug Cage 

Results from the Jug Cage in Blue Hole are summarized 
in Figure 24, On June 6, shortly after the Jug Cage was 
installed, the amount of Sagittaria leaf biomass in a sample 
taken inside the cage (2 40 grams /m"") was about the same as 

the amount of leaf biomass in a sample taken from the 

2 
Sagittaria bed surrounding the cage (220 grams/m ). On 

September 11, after two months of protection, a sample of 

leaf blades clipped from within the cage weighed over 300 

grams/m , whereas the biomass of a sample taken from the un- 

2 
protected area outside the cage was less than 200 grams/m . 

The biomass differences of the inside-outside cage 
samples can be attributed to differences in the size of 
individual leaves, not in the number of leaves. As Figure 
24 shows, the number of leaf blades in the sample clipped 
from the floor of the cage on September 11 was actually less 
than the number of leaves in the sample taken from outside 
the cage. The length of leaves inside the cage, however, 
was much greater than leaf lengths in the surrounding bed. 

Figure 24A, describing the frequency distribution of 
leaf lengths, shows that the lengths of cage leaves were dis- 
tributed relatively evenly over size classes ranging from 
0-9 to 80-89 centimeters. In contrast, the leaf lengths of 
the outside sample showed a skewed distribution with a modal 
size class of 10-19 centimeters and class range of 0-9 to 
50-59 centimeters. 



1600 

M 1280 
6 

o 960 • 



u 320 



JUG CAGE 
Sagittoria kurziano 

9-11-78 



Q 



l~i Inside cage 
E^ Outside cage 



XL 



0-9 ' 10-19 ' 20-29 ' 30-39 ' 40-49 ' 50-59 60-69 ' 70-79 80-89 90-99 '100-109 



6 4 



ui ' 

> 
< 
u 



B 
9-11-78 



LENGTH CLASS (cm) 
_ 400r 



in g 
3"S.300H 

i»200f- 

u. -e 

< c 100 

UJ s 

^i 



C 
7-«-78 



O — 



O 



9-11-78 



F3 



.SiL. 



2 • 
O £ 



Figure 24, Characteristics of Sagittaria leaves sampled 

both inside and outside of Jug Cage. A. Size 
distribution of inside-outside leaf samples. 
B. Numbers of leaves of inside-outside 
samples. C. Weight of leaves of inside- 
outside samples. 



77 



Run Cage 

The biomass, number, and size of Sagittaria leaves 
cut inside and outside the Run Cage are shown in Figure 25. 
The niiinber of leaves in the two samples were about equal, 
but they differed greatly in size and biomass. After three 
months of protection, cage leaves weighed about 450 grams/m , 
and were distributed over a wide range of length classes 
with maximum lengths between 10 and 109 centimeters. The 
Sagittaria leaves in the surrounding bed appeared to be 
stunted. They averaged about 2 5 centimeters in length, and 
measured only 6 centimeters at the maximum. The biomass 
of the outside sample was about 300 grams/m , considerably 
less than the inside sample. 

Over the summer (May 2 9 to September 12), Sagittaria 

2 
plants colonized 0.55 m of the open sand area in the Run 

Cage (Fig. 25). The 347 new clumps produced during this 

period accounted for a net biomass accumulation of 2 02.7 

grams. As is evident in the figure, the increase in 

Sagittaria cover was greater on the downstream side of the 

cage than on the side facing the flow. 

Another feature which distinguished the inside cage 

sample from the outside sample was the color and texture of 

leaf blades. Leaves cut from the cage were bright green 

and smooth. Leaves from the surrounding bed were brownish 

and gritty. Results from ashing showed that the organic 

weight of cage leaves was about 8 3% of their dry weight; 



78 



1600 



y 1280 

> 

2 960 



O 640 

UJ 

m 320 

2 



. D Inside cogt ^ 

Cx] Outsid« cage 



RUN CAGE 
Sogittaria kurziano 

9-11-78 



0-9 I ;0-l9 I 20-2S I 30-39 I 40-49 I 50-59 I 60-69 

LENGTH CLASS (cm ) 



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Sogittaria Colonization 




GROWTH 

EDGE OF BED 

• — • 5-29-78 

7-6-78 

O — O 9-12-78 



cm 
20 



Figure 25. Sagilrtaria colonization and characteristics of leaves 
sampled both inside and outside of the Run Cage. 
A. Distribution of leaf lengths of inside-outside 
samples. B. Weight of leaves of inside-outside 
samples. C. Numbers of leaves of inside-outside 
samples. D. Colonization of open cage bottom by 
Sagittaria plants. 



79 



the organic weight of leaves sampled outside the cage was 
only about 6 3% of dry weight. Microscopic inspection of 
the residue remaining after ignition showed, for the cage 
sample, a clean white ash. The residue from the outside 
sample was grayish in appearance, and consisted of relatively 
large sand grains in addition to ash and other mineral 
matter. 

Sediment Deposition 

There was a considerable buildup of sediment in both 
cages following installation. In the Jug Cage, sediment 
depth increased 5.8 centimeters between May 29 and July 6, 
1978. In the Run Cage, sediment depth increased 1 . ii centi- 
meters between May 2 9 and June 30. 

Response to Repeated Cutting 
Figure 26 shows the regrowth patterns of Sagittaria 
plots subjected to varying intensities of cutting over a 
four-month period extending from February 2 to June 13, 
197 3. Plots that were cut six times previous to the test 
recovery period (June 13 to July 21) regrew just as 
rapidly as plots that were cut three times or only once. 
The figure also shows that the average growth rate (slope) 
of plants cut every two to three weeks increased after each 
successive cutting. 

Following the first cut on February 20, Sagittaria leaf 
blades grew back at an average rate of 0.^8 grams/m'^/day 



80 



REPEATED CUTTING 



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Sagittaria kurziana 


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February ' March 



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June 



MONTH 



Figure 23. Sagittaria leaf recovery in plots subjected tc 
repeated cutting. Three plots (0.12 5 m^) were 
used for each of three Treatments: 1. plots 
cut every 2-3 weeks, 2 



weeks 



ind 3 



plots cut every M--6 
plots cut after four rr^onths . 



81 



over the ensuing 15 -day period. The same plots recovered 

2 
at an average rate of 3.7 grams/m /day after the last cutting 

on June 13. This rate is comparable (no significant differ- 

ence) to the rates of 3.6 and 3.8 grams/m /day measured for 

plots cut three times and only once, respectively, prior to 

the test recovery period. The growth rate of three new 

plots, cut on June 18 and harvested July 28, was 3.0 grams/ 

2 
m /day. 



Fauna Survey/ 

Invertebrates 

Mollusks . Table t+ summarizes the results of the inver- 
tebrate sampling in areas subject to varying degrees of 
disturbance. The table shows that one of the samples from 
the Headsprings Exclosure (No. 1), which at the time of the 
survey had been undisturbed for over two months , contained 
more species (4) and greater numbers (about 17,000/m'') and 
biomass (about 720 gramLs/m , including shell weight) of 
mollusks than any other sample. Each of the other five sam- 
ples contained fewer species, and less than half this number 
or biomass. Of these, the sample taken from the moderately 
disturbed Chara bed below the Third Dock (No. 5) contained 
the greatest snail biomass. The number of snails in the 
other Third Dock sample site (No. S), a badly torn Chara 
bed, was similar to the number found in a sample (No. M-) 
taken from a less disturbed bed in the Second Dock Exclosure. 



82 



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' 84 

The weight and numbers of mollusks does not appear to 
be related to the amount of vegetation at a site. Maximum 
numbers and weight were found in a sample (Headsprings 
Exclosure, No. 1) which ranked fourth in weight of plant 
material. In contrast, the second sample in the Headsprings 
Exclosure (No. 2) contained the most plant material, but 
ranked fourth in both number and biomass of mollusks. 

Arthropods . Table 4 shows that both the number and 
biomass of arthropods in the sample taken from the heavily 
disturbed Chara bed (Third Dock, No. 6) were considerably 
lower than the number and biomass of samples taken in other 
areas. This sample contained two insect larvae and two 

small shrimp, which collectively weighed 0.08 grams (sampling 

2 o 

area 0.017 7 m ) or 4- . 5 grams freshweight/m . A second sample 

taken from a less trampled portion of the same bed (Third 
Dock, No. 5), contained a Trichopteran (Caddis fly) larvae. 
5 small crayfish, and 7 shrimp, which collectively weighed 
0.76 grams, or 43 grams freshweight/m''. The biomass of 
arthropods sampled in the two fenced areas , the Headsprings 
Exclosure and Second Dock Exclosure, was about the same as 
that found in Third Dock, No. 5, with the exception of sam- 
ple No. 3, Second Dock Exclosure, which weighed 1.0 4 grains. 

Fish 

Results of rhe fish survey are summarized in Table 5 , 
which shews the types and numbers of fish and other aquatic 



8 5 





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87 

organisms in protected and unprotected areas of the Head- 
springs Run. The majority of fish observed were represented 
by two families, the sunfish fam.ily, the Centrachidae , and 
the minnow family, the Cyprinidae. The table shows that 
whereas only one Cyprinid species, the common chub, Hybopsis 
harperi , was seen in the disturbed area below the First Dock, 
several members of this family, including chubs; chubsuckers , 
Erimyson sucetta ; suckers, ' Koxostoma sp . ; and golden 
shiner, Notemigonus crysoleucas were seen inside the fenced 
exclosure. The figure also shows that two species of turtle, 
the loggerhead musk, Sternothaerus minor , and yellow-bellied, 
Pseudemys scripta , were observed in the exclosure. No 
turtles were seen on four 2 -meter runs in the area below 
First Dock. 

The numbers of Centrachids also differed greatly in the 
two study areas. Large congregations of bass ( Mi crept srus 
spp.I and bream. ( Lepomis spp.) were commonly observed in the 
Headsprings Exclosure under the shelter of aquatic olants or 
overhanging shrubbery. In the First Dock area, where much 
of the vegetation had been trampled out, the few bass and 
bream counted were generally observed feeding or resting 
alone or in pairs. Despite heavy disturbance, crayfish were 
seen near the First Dock during the survey. Although no 
crayfish were seen in the exclosure during the four survey 
runs, they were frequently observed in this area during work 
on other aspects of the study. 



- ,^:~-.. .-. 



DISCUSSION 

In the Headsprings Reach, the loss of plant cover 
resulting from recreational use is more visibly apparent 
than is the loss of cover in either the Rice Marsh or Flood- 
plain Reach. The data show, in fact, that the percentage 
loss of standing crop in the Headsprings Reach is much 
greater than the percentage loss in the middle and lower 
reaches. For this reason, details of the impact of recre- 
ation on the plant communities of the Headsprings Reach are 
discussed first, followed by the impact of recreation on 
the plant communities of the Rice Marsh and Floodplain 
Reach; the impact of recreation on the animals of the river; 
and the carrying capacity for recreational use. 

Impact of Recreation on 
the Plant Communities of the~Tieadsprings Reach 

Tuber Impact 

The three sections of the Headsprings Run v/hich were 
mapped in April, 19 78, and remapped in September, 1978, show 
that there is a large loss of plant cover in this reach in 
summ.er. A more detailed analysis of the data from the plant 
damage survey reveals aspects cf tuber impact which were not 
shown in the figures included in rhe Results section. 
Figures 10 and 11 in the Results section suggest that tuber 



88 



89 

damage may actually decline during the days and hours of 
heaviest use. This suggestion is very misleading. The data 
for the busiest days and hours were collected in July and 
August, the last two months of the summez-" survey (April - 
August). By that time, a substantial amount of vegetation 
had been trampled from the channel, such that the amounts of 
netted plants seemed small relative to the magnitude of use. 

Figure 2 7 shows the amounts of daily use and damage, 
and Figure 28, the amounts of hourly use and damage, for 
each of the five days surveyed in summer, 19 78. Three 
important features of user impact are described in these 
figures : 

1. The ratio of daily damage to daily use, or average 
amount of plant damage per user, declined sharply 
over the summer (this ratio can be roughly esti- 
mated by comparing the heights of the bars in 
Figure 27) . 

2. The ratio of hourly damage to hourly use declined 
over the summer (this was determined from the 
slopes of the graphs in Figure 28). 

3. On Wednesday, June 14, the only weekday surveyed, 
hourly amounts of plant damage remained consis- 

■: tently low, and were not correlated (r2= 0.01) 
with the amount of hourly use. 
The trends described in Figures 2 7 and 2 8 can be large- 
ly accounted for by two factors : 1 . tuber behavior and 2 . 
the physical characteristics of the Headsprings Reach. 



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200 400 600 800 1000 



3000 r 



Users 
QOomage 




3O0O 



200 400 600 300 1000 
USERS Uio/hr) 



4-22 S-14 3-5 

5-21 7-9 



- 2000 
1000 




Figur? 



23. Amounts of hourly use and plant damage for 

five survey days, Headsprings Reach, April to 
August, 19 78. For each survey day, the rela- 
tionship of hourly damage (y) to hourly use (x) 
is described by a linear equation: M--22-78, 

^ = 0.72); 5-21-78, 

= 0.20; 6-14-78, (r^ = 



y = 70.8 + 0.70X (r' 



y = 80 
7-9-78 



3 + 0,7 Ox (r 
y = 72.8 + 



■7 



01) ; 



y = -5.2 + 0.39x (r 



31x (r- = 0.90) : 8-5-7i 



: 0.89) . A large raft of 
Cicuta (9 88 g, dry wt . ) netted on 7-9-7 8 was not 
included in data for 11 a.m. -12 noon (733 users). 



92 



Recall that this reach averages about 10 meters in V7idth 
and is generally less than 1 meter deep. On quiet weekdays, 
when generally fewer than 10 users enter the run each hour 
(see June 14-, Figure 28), an individual tuber or group can 
enter the narrow run and proceed downstream without inter- 
ference from other groups or individuals . As shown by the 
amounts of plant material netted, hourly damage remained 
consistently low, less than 50 grams, over the course of 
this weekday. 

On summer weekends, when the amounts of hourly use 
range from 100/hr. to as high as 1000/hr., groups of users 
inevitably become tangled around the entry docks , and 
bottlenecks of tubers develop over the course of the Run. 
Unable to proceed downstream, or forced to the side of the 
channel, many users get off their tubes and trample through 
the shallow channel in their attempts to rejoin their party 
or resume progress downstream. The amount of hourly plant 
damage increases directly as the amount of trampling and 
congestion increases . 

Another problem occurs at the junction of the Head- 
springs Run and Blue Hole, iMany tubers, arriving at this 
point, choose to proceed up the Blue Hole channel against 
the direction of the outflow. Unable to paddle against the 
strong current, many ger off their tubes and walk up the 
edge, the path of least resistance. This acxivity results 
in extensive trampling of both the plant beds and sediment 
banks along the edge of the Blue Hole run. 



93 

Plates 2 and 3 visually document the types ox damage 
which have been discussed, and demonstrata, convincingly, 
that the decline in netted drift in the later summer months 
is a result of severe environmental degradation rather rhan 
a change in tuber behavior. 

Species Damaged by Tubing 

Figure 29, showing species damage in the Headsprings 
Reach in S'ommer , illustrates other importanr aspecxs of 
tuber impact. Three trends can be discerned: 1. for 
one species. Chara, borh the amount netted and ixs percent- 
age of the total damage increased in the later survey months 
(July and August); 2, for thr^ee species, Ludwigia . 
Nasturtium , and Cerarophyllum , the amounxs ne'cted and their 
percentage of total damage decreased in the larer survey 
months ; and 3 . for the remaining species , the amounts and 
percentages eirher rem.ained fairly constant or were highly- 
variable over the summer survey. 

Chara damage . Figure 2 9 shows that very little Chara , 
generally less rhan 20 grams, was netted on the April, Ma-y , 
and June survey days. However, 10 and 330 gram.s were 
nexted on July 9 and August 5, respectively. As previously 
stated, the da~a for this soecies are more likely a reflec- 
tion of method than actual tuber impact. The substantial 
increase on Ajugust 5 undoubtedly resulted from an improve- 
ment in the method, which was achieved by adding a third 
netting assistant, specifically assigned to collect all 



Plate 2. Tuber impact on the Blue Hole. A. Bank and 

bottom erosion due to trampling. B. Disturbed 
and protected sections of a Sagittaria bed showing 
differences in both the length and color of plant 
blades. In the cage, leaves measure to 1 meter in 
length and are light green. In the surrounding 
bed, average leaf length is about 0.3 meter, and 
the blades are discolored by adherent silt and 
other mineral matter. 




B 






•^-v<'/^ 




ri-Sfc 



This bed 



^^^^^ - Sagittarid bed, April and Aus^ust, 1973. ...^^ ^^., 
situated at rhe outlet of the Blue Hole xRun , was ' 
phouographed rrom approximately the same position 
at the start or the tubing season in April" (A.) ar^d 
later in August (B). In April, the olants stood" 
Knee ro waist high; by August thev had been tramt^ed 
down to ankle height. 



98 



1000 

800 

600 

I 400 

» 200 



j;; 1000 1 



800- 



600 
400 
200 








/ 
i 



Sagiitoria 



1 



CiCutQ 



Aon 



7T 



rri 



^ai > June ' 
MONTH 



r30 1 000 
SO 300 
SOO 



/ 
/ 



40 



20 



30 



60 



•40 



20 



_Ctn_ 



July ' August 



Zizonia 



400 
2 00 





lOOOi 
800 

SOO 
400 
200 





m 



Chora 



rs-a ciq_ 



Ik 



April ' May ' jun« ' July ' AuqusI 
MONTH 



r80 
60 
40 

20 < 

a 

-J 

2 
p 

u. 
-80 O 

UJ 

■SO « 

Ui 

a. 
-40 

•20 





z 

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2 




April I May I June I July ' August 
MONTH 



100 
80 
60 
40- 
20 




Nasrurrium 



100- 
30 

SO 
40 
20 





Th rm 



CerQfopftyilum 



XbjL. 



Im. 



1-3 
i 

1-6 



r3 



I j Amount netted 

L^ Percent of total damage 



Aoril ' May ' June l Juiy > August 
MONTH 



O 

z 
u 
u 
a: 

UJ 



Figure 29. Species damage in the Headsprings Reach, 
April tc August, 19 78. 



99 



drift below the surface. Interestingly, under more efficient 
capture, the amount netted on August 5, 333 grams or 30% of 
the total damage , was proportional to the standing crop of 
this species, which was 3 3% of the total standing crop in 
the survey area. 

Ludwigia, Nasturtium, and Ceratophyllum damage . Damage 
to Ludwigia, Nasturtium-, and Ceratophyllum was heaviest in 
early summer, then declined over the succeeding months. Two 
characteristics, shared by all three species,, likely account 
for this pattern of damage: 1. Ludwigia , Nasturtium , and 
Ceratophyllum have the smallest standing crops of all the 
species mapped in the Headsprings Reach (see Appendix D) . 
2. All three species possess weak stems which are vulnerable 
to tearing, as was shown for Ludwigia and Nasturtium in the 
Resistance Experiment, and as is a commonly cited character- 
istic of rootless Ceratophyllum (Arber 192C, Sculthcrpe 
1967). Because of these shared characteristics, rhe bar 
graph suggests that these three species were almost com- 
pletely trampled out of the Headsprings Run in the early 
summer months , such that by July and August they were 
scarcely noted in the drift. Note that nearly 10 dry grams 
of Ludwigia , which is about 2.5% of the total standing crop 
of this species Cabout 4000 grams, measured in winter), was 
netted during a six-hour period on Saturday, May 21, 19 78. 
The amount of Ceratophyllum netted in four hours on April 2 2 
accounted for 2.3% of its total winter standing croD . 



100 



Assuming that as much as 4-5% of the standing crop of 
these plants are damaged in a single day on spring weekends, 
one can easily comprehend their near-eradication by mid- 
summer, as the survey data suggest. Note, in map section H 
(Fig. 15), the large loss of Cerat'ophyllum cover between 
April and September, and observe the disappearance of 
Ludwigia and liasturtium in map sections Q and Pw 

Damage to other species . Sagittaria , Zizania , 
Myriophyllum , and Cicuta all have relatively large standing 
crops, ranging from 2 kilograms for Myriophyllum to 150 
kilograms for Sagittaria . Although these species sustained 
heavy damage, inspection of the Run and Blue Hole at the 
end of the summer showed that some cover remained. This is 
evident in the August map of Blue Hole CFig. 5) , which shows 
Sagittaria growing in the center of the spring run channel 
and along the south edge of the pool. Like Sagittaria , 
Zizania sustained a heavy loss of cover in sunmier. Many 
surviving plants, however, were seen growing along the edge 
of the Headsprings Run the following fall , 

Figure 2 9 shows that Cicuta damage was highly variable, 
being negligible on three survey days , but accounting for 
a large proportion of the total damage on the other two 
survey days C3Q% on April 22, and 45% on July 9). The 
variable nature of Cicuta damage is likely due to its growth 
habit. Cicuta beds, which grow along the edge of the 
channel^ are comprised of numerous leafy stems interconnected 



101 

by a network of large floating rhizomes. Under light dis- 
turbance, small leaf and stem fragments may break off, but 
the bulk of the bed remains in place. Under heavy distur- 
bance, however, an entire floating bed may be dislodged and 
set adrift. The large amount of Cicuta netted on July 9, 
about 1 kilogram dry weight, resulted from the displacement 
of a single raft of this species. 

Impact of Divers on the Blue Hole in Winter 

Data from both the plant damage survey and experimental 
growth plots strongly suggest that the Sagittaria community 
in the Blue Hole loses more cover in winter than it can 
regain by regrowth. As previously stated, the Blue Hols is 
a very popular winter diving area, and most of the Sagittaria 
damage observed there can be directly attributed to that 
activity. 

A comparison of the amount of Sagittaria damaged by 
winter divers with the amounts damaged by summer tubers 
shows that although the overall magnitude of damage is 
greater in summer, the impact of an individual diver is 
much greater than the impact of an individual tuber. On 
March 3, 3 8 divers uprooted and tore about 5 00 grams of 
Sagittaria , an average of about 5 grams/diver. On May 21, 
12Q0 tubers were counted and about 300 grams of Sagittaria 
netted from the Blue Hole area. Although the overall amount 
of damage was greater, the amount per user, about 0.75 gra^m, 
was much less . 



102 



Figure 30, which shows the damage and recovery rates 
of both uprooted and torn Sagittaria plants, clearly illus- 
trates the problem of this large individual impact. At a 
level of about 50 divers/^ hrs , (the netting period), the 
amount of Sagittaria uprooted is about equal to the recovery 
rate of plots that were experimentally uprooted in winter. 
Further inspection shows that at a level of 100 divers, the 
amount or damage , about . 3 gvam/m" , exceeds the daily 
recovery rate (about 0.0 3 gram/m /day) by an order of 
magnitude . 

Figure 31 shows another important aspect of diving 
impact on the Sagittaria community of the Blue Hole. The 
histogram shows that divers are uprooting smaller and/ or 
younger plants. Recall from the Resistance Experiment that 
small plants are particularly vulnerable to uprooting due t:o 
a shallow root system and the lack of a deep sediment cover. 
In the Blue Hole, the source of these small, young plants 
is readily identifiable. They arise from runners which ax- 
tend from the margins of Sagittaria beds into the open sand 
areas of the channel and pool. 

The type of damage shown in Figure 31, and the amounts 
shown in Figure 30, indicate that divers are uprooting a 
very large number of colonizing Sagittaria plants. This 
suggests that divers, in trampling back the edges of 
Sagittaria beds, are preventing winter regrowth, and are 
adding further to the deterioration and loss of Sagittaria 
cover in the Blue Hole. 



r ii'i^l^'i 1-1 



103 



0.5 



0.4 - 



o 

13 
«^ 

6 

w 0.3 

"J 
>^ 
■a 



Recovery rate- cut plots 



Sflgjtrqrig kurziona 



Amount torn 
Amount uprooted 



O 

< 

< 
Q 



0.2 - 



0.1 



/ 



Recovery rate -uprooted plots 



10 



20 



_L 



30 



40 50 60 
DIVERS(no./day) 



70 



80 



90 



100 



Figure 30. 



Amounts of Sagittaria torn and uprooted over 
various levels of diving activity, and the 
winter recovery rates of plots experimentally 
subjected to tearing and uprooting. The rela- 
tionship^ of damage (y) to number of divers (x) 
is described by an exponential equation: 

amount torn, y = 2.74e°-°^^; amount uprooted, 

y = l.USe ' . The winter recovery rares 
represent the average growth rate over a 2 9- 
day period extending from February 2 2 to March 
21, 1978. 



104 



500 1 



400- 



u. 

o 

(E 
Ul 
IS 

Z 



300 



200- 



100 



I I Neited 1-29-78 

Userj 6S0i»er),l3 Canoes 

Q Netted 3-4-78 

Ulerj 98 Divert, 4 Conoej 

Q Sampled from Oeoils ti* Excloeure 
No users 



SagittcrJa kurziana 




30-39 I 40-49 150-591 60-69 i 70 
LENGTH CLASS (cm) 



Mn 



a=3 Qzi 

-79 I 80-39 I 



-^ 



90-99 I 



Figure 31. 



Size distribution of Sagittaria clumps 
uprooted by divers compared to the size 
distribution of clumps sampled from the 
Devil's Eye Exclosure , which receives no 
use . 



105 



To conclude the discussion of diving impact on the Blue 
Hole in winter, one other important research result will be 
considered: The exponential pattern of damage shown in 
Figure 30. The location of the netting site just below the 
Blue Hole outlet enabled me to simultaneously measure plant 
damage and observe divers. As the survey progressed over 
the winter 1977-78, it became apparent that heavy Sagittaria 
damage occurred on days when the Blue Hole area was conges- 
ted with scuba divers and snorklers . This congestion almost 
always occurred around midday (11 a.m. to 2 p.m.) and 
resulted from: 1. large diving groups (dive class groups 
and dive clubs with 50 or more individuals regularly visit 
the Springs) and 2. the concurrent use of the area by many 
smaller-sized groups (10-15 divers/group were commonly 
observed) . 

Jug Spring, with the deep cavern that divers like to 
explore, can accommodate, .only a limited amount of use at a 
given time. On busy days, many scuba divers are forced to 
wait in the surrounding pool or around the dock area until 
the Jug has cleared. Some individuals, heedless of the 
potential for damage, retreat to the edge of the pool where 
the remaining Sagittaria grows . Others tramp and swim about 
actively, uprooting and tearing large amounts of plants 
Csome do this whether they ai-^e waiting to dive the Jug or 
not) . 

An additional problem, which was mentioned in the dis- 
cussion of summer damage, is the fact that many divers, 



106 



arriving at the Blue Hole outlet, choose to walk up the 
sides of the channel rather than swim against the current. 

On quiet days, when smaller and/or fewer groups use the 
resource, the amount of plant damage decreases considerably 
as some of the above problems are eliminated. An individual 
or small diving group can enter the Blue Hole and, without 
interference, descend the Jug, explore the submerged cavern, 
and exit from the area. Of course, individual responsibility 
or lack of it is an important impact factor on both quiet 
and busy days. 

Winter Recovery in the Headsprings Run 

The previous section showed that divers tear and uproot 
large amounts of Sagittaria in the Blue Hole, hastening the ■ 
deterioration of this area. However, as the following dis- 
cussion suggests , winter diving does not appear to have 
much impact on the Headsprings Run , defined as that portion 
of the river between the Headsprings and the Blue Hole . 
This does not imply that divers cause no damage, but that 
the amounts torn and uprooted (Fig. 8) do not exceed the 
amounts recovered by winter regrowth. 

The sections of the Headsprings Run that were mapped in 
November-December, 1977, and remapped in April, 19 78, (Fig. 
15) show a considerably gain in plant cover over this four- 
month period. A review of the results from experimental 
plots, exclosures, and mapping suggests ways in which this 
recovery occurred. 



107 



Chara recovery . The modest regrowth of Chara in the 
Second Dock Exclosure (Fig. 22) appears to contradict the 
suggestion of rapid recovery in map section R (Fig. 15) 

located just below the Third Dock. Planimetric measurement 

2 2 

showed that Chara increased from 1.1 m in July to 2.0 m 

in October in the Second Dock Exclosure. In map section R, 

2 2 
Chara increased from 10 m to 22 m between December and 

April. The average rate of expansion of the Second Dock 

bed, relative to the length of edge at the start of mapping, 

2 
was 3 7 cm /m/day. The average rate of expansion of the 

2 
Third Dock bed (map section R) was 86 cm /m/day. 

Although several factors, such as winter leaf fall, 
current, and depth (which was about the same in both areas) 
could account for these differences , I believe that the 
critical factor is the degree of site disturbance. Although 
map section R was mapped carefully in December, 1977, the 
substrate was not examined for fragmentary plant remains . 
When this section was remapped the following September, the 
substrate was carefully examined and found to contain many 
small Chara fragm.ents . It appears that growth from frag- 
ments , a characteristic of Chara (Tarver 1978), supplemented 
the lateral outgrowth of the major bed in producing the 
large cover increase below Third Dock,. In contrast, there 
were virtually no Chara fragments in the thoroughly trampled 
sand areas of the quadrats surveyed in the Second Dock 
Exclosure, and lateral outgrowth was the only type of 
regrowth observed. If due to the absence of fragmentary 



108 

remains in the substrate, the slow recovery rate of Char a 
in the Second Dock Exclosure has important implications for 
the regrowth of the other areas which have been trampled 
into a similar condition. 

Zizania recovery . The winter recovery of Z'izania was 
fairly extensive in those areas that were mapped in November- 
December, 1977, and remapped in April, 1978. Two regrowth 
mechanisms may be responsible for the observed recovery: 
1. winter seeding and 2. growth from buried stem fragments. 

While netting plants January 14, 1978, I observed a 
large number of floating Zizania seeds in the drift. The 
source of these seeds was undoubtedly the fruiting culms of 
emergent plants which grow upstream along the shallow edges 
of the Headsprings Run. The mere presence of seeds, however, 
does not necessarily lead to seedling establishemnt . 
Sculthorpe C1967) related that Zizania seeds, shed from 
culms by wind, float for a period of time before the};- sink. 
One would intuitively expect that seeds shed along the Run 
would be rapidly transported downstream before they could 
sink and germinate. Recall that the results from the Second 
Dock Exclosure showed only a single instance of Zizania 
colonization (.quadrat 3) that could be ascribed to seeding. 
At least in that area, seeding did not appear to contribute 
significantly to the spread of this species in the channel. 

A second potential source of Zizania plants is the 
remains of stem material buried in the substrate. A 



109 

Zizania biomass sample showed that this species develops a 
mat-like layer of stems and roots below the mud surface. 
Although the above-ground parts of this plant may be com- . 
pletely removed in some areas, inspection of the substrate 
often shows the fragmentary remains of a root mat . Growth 
from viable stem, fragments embedded in the mat could account 
for much of the recovery seen in the Run in winter. The 
results from the experimental Zizania plot in the Headsprings 
Exclosure seem to support this suggestion. Although the 
above-ground parts of cut plants did not recover, a new 
seedling, which had grown up in the quadrat, appears to 
have risen from a buried root mat below. 

The recovery of Ludwigia, Nasturtium, Ceratophyllum , 
and Nyriophyllum . The discussion of tuber impact in the 
Headsprings Reach emphasized that fragile, low-standing-crop 
species, such as Ludwigia , Nasturtium , and Ceratophyllum , 
sustain very heavy cover losses in the spring and early 
summer. By midsummer, these plants have largely disappeared 
from the trampled channel. They do, however, recover to a 
degree in winter, as shown in map sections H, Q, and R. A 
consideration of the growth characteristics of these plants 
as well as those of Kyriophyllum shows that they possess 
mechanisms which enable them to survive in this unstable 
area. All of these species are able to regenerate from stem 
and/or leaf fragments CArber 1920, Sculthorpe 1967, Haslam 
1978) and generally exhibit rapid growth rates as shown by 
this study. 



110 



The ability of Kyriophyllum and Ceratophyllum to grow 
from fragments was observed in our work. Fragments of 
these plants were seen trailing from stakes shortly after 
they had been driven into the channel floor of the Second 
Dock Exclosure, One Myriophyllum fragment, which was cap- 
tured near the base of a stake, secured itself to the under- 
lying substrate by developing numerous adventitious roots 
along stem nodes. Although Ceratophyllum does not possess 
roots (Arber 1920), plants of this species were seen growing 
vigorously while suspended from stakes, fencing, and other 
submerged obstacles. Rapid growth rates have been measured 
for both these species. In our study, cut Myriophyllum 
plots recovered more than 50% of their original above-ground 
biomass one month after cutting, in both summer and winter 
plots. Odum C1957) reported winter growth rates as high as 

r\ ...... 

2 5 dry grams/m /day for Cer at ophy 1 lum plants growing in a 
submerged cage at Silver Springs . 

Commercial growers of watercress , Nasturtium officinale , 
have long taken advantage of the regenerative abilities of 
this plant CKaslam 1978). In addition to rooting at stem 
nodes CTarver 1978), this species is able to produce an 
entire plant from a single detached leaf (Sculthorpe 1967). 
At the Ichetucknee, the tremendous growth of this plant on 
the lower fence of the Headsprings Exclosure attests to its 
powers of propagation and suggests a very rapid growth rate. 



Ill 



In view of these characteristics , it is not surprising 
that all of these species exhibited some winter recovery 
(Dec. -April) in the map sections- H, Q, and R (Fig. 15). 
Note the increase in Ceratophyllum cover in section K and 
the growth of Nasturtium in section Q. Ludwigia and 
Myriophyllum recovery is also evident in these map sections. 

This discussion of species recovery in winter has 
described both actual and potential regrowth in the Head- 
springs Run. This information, however, must be interpreted 
with caution. Regrowth from stem and/or leaf fragments, 
whcih is characteristic of Nasturtium , Ludwigia , 
Ceratophyllum , and >fyriophyllum depends on: 1. an upstream 
source of plant material and 2 . the presence of submerged 
obstacles, sediment deposits, or plant beds which either 
snag fragments or reduce current locally, enabling coloni- 
zation. The regrowth of Chara or Z'izania , which are able 
to reproduce from buried stems (or cortical cells in the 
case of Chara ) , require a substrate containing viable 
reproductive parts . 

These prerequisites for regeneration, however, appear 
to be diminishing in the upper reaches of the Ichetucknee 
River. Park officials have noted that winter regrowth has 
progresively decreased over the past several years. Also, 
the map-remap sections represent only a small fraction of 
the Headsprings Run. In some areas, virtually no recovery 
was noted over the winter of 1977-78. 



112 



The low-standing-crop species, such as Ludwigi a, 
Nasturtium , and Ceratophyllum , may not be able to sustain 
recovery in the future. It hardly needs to be emphasized 
that once the upstream sources of these plants are depleted, 
colonization of the Run from downstream beds would be ex- 
tremely slow, as it would depend on dispersal agents other 
than current , such as human or animal transport . 

As previously suggested, the winter recovery of Chara 
and Zizania appears to be dependent on the ccndirion of the 
substrate. As more areas of the Run become reduced to 
sterile sand and limerock (Plate 4), which has been the long- 
term trend in this area, the recovery of these two species 
will undoubtedly diminish. 

Impact of Recreation on the Plant Communities of 
the Rice Marsh and Floodplain Reach 

The results of the summer damage survey showed that, 
relative to the amount of plant cover, the Headsprings Reach 
sustains greater plant damage than either rhe Rica Marsh or 
Floodplain Reach. Figure 3 2 extends rhis analysis further: 
it shows, for each reach, a Damage Index which is defined 
as the mean hourly fractional loss per user (the fraction 
of standing crop that, on the average, is damaged by one 
user in one hour). An interesting pattern can be seen in 
this figure; the Damage Index declines by a constant percent- 
age in a downstream fashion from the Keadscrings Reach to 
the middle and lower reaches. The Damage Index of the 



Plate t+, Channel erosion in the Second Dock area. All plant 
material has been trampled out of the substrate, 
which, in the most extreme case, has been eroded 
down to lim.erock. 



114 



t° 





115 



5. On 



4.0- 



X 

UJ 

Q 3.0- 



UJ 

o 

< 

§ 2.0- 



1.0- 



Headsprings Rice Marsh Floodplain 
REACH 



FigTire 32. Damage Index for three reaches of the- 
Ichetucknee River. For each reach, 
Damage Index = 

mean plant damage ( grams )/hr. x 10^ 

standing crop (grams) x mean no. of users /hr, 



116 

Headsprings Reach ( M- . 8 ) is about twice that of the Rice 
iMarsh (2.5), which is twice that of the Floodplain Reach 
(1.2). The differential impact suggested by the Damage 
Index is consistent with the observation that recreational 
activity in the middle and lower reaches does not generally 
result in the extensive damage that is so evident in the 
Headsprings Reach. While snorkling the river in October, 
1978, I noted very few torn and uprooted beds over the ^- 
kilometer portion of river bounded by the Rice Marsh and 
Floodplain. 

A number of factors could account for the downstream, 
exponential decline in the Damage Index. These factors may 
be roughly classified as environmental or behavioral. 
Environm.ental factors would include: water depth, temper- 
ature, river width, length of reach, rate of flow, amount 
of incident light, size of standing crop, amount of cover, 
and many other variables. Behavioral factors would include 
such variables as user attitude, user energy, tim.e on river, 
and tolerance to cold water. Of course, many of these 
factors are not independent, such as cold tolerance and time 
on river. 

Figure 3 3 shows the relationship of the Damage Index 
to variable environmental and behavioral factors. Some 
factors, which one would intuitively expect to be operative 
in reducing user impact , do not appear to be related to the 
Damage Index. Two, for example, are water depth and width. 
As previously discussed, these factors undoubtedly contribute 



117 



4H 
X 

a 
2 3 

LlI 

o 

< 

2 2 

< 

Q 



l-VA 




IT 



IE 



I 1.5 2.0 

MEAN DEPTH (meters) 



5n 



4 - 



I - 



HE 



WA- 
10 15 20 

MEAN WIDTH (meters) 



X 

lU 

a 



< 

< 



5t 



4- 



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5i 



4- 



3- 



I - 



IK 



3000 6000 9000 
TOTAL PLANT COVER (m^ ) 



O^V/ 
2000 



H 



20 40 60 
PERCENT COVER 



Figure 33. Damage Index relared to physical charac- 
teristics of the river and behavioral 
characteristics of use. The velocity 

of flow in the Rice Marsh (II, ) was 

estimated as an intermediate value between 
that of the Floodplain and Headsprings 
Reach. 



113 



4- 



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9 3 



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o 

< 



< 
a 





I 




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IL 




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nr 




U 1 


• 


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C 


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5 


.0 


1.00 1 


.50 2. 



0.5 1.0 1.5 2.0 
LENGTH OF REACH (miles) VELOCITY OF FLOW (cm./sec.) 



X 

Q 



LlJ 
O 
< 

< 

a 



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I 












4- 








3- 








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TIME ON RiVER (hrs.) 



















4- 








3- 
















H 


2- 










HE 


















1 ■ 

n 

















USER ENERGY 
TOLERANCE TO COLD WATER 



Figure 33. Damage Index related to physical charac- 
teristics of the river and behavioral 
characteristics of use (continued). 



119 

to the damage in the narrow and shallow Headsprings Reach. 
Yet, they should not be considered the sole determinants of 
recreational impact. The analysis shows that the Damage 
Index was greater in the deepest and widest reach, the Rice 
Marsh, than in the shallower, and slightly narrower Flood- 
plain Reach. 

Our observations, as well as those of Park personnel, 
suggest that increasing fatigue and decreasing tolerance to 
cold water are important in reducing recreational impact in 
the lower reach of a 5^-kilometer or SJ^-mile river. Many 
tubers, arriving at the Floodplain Reach, appear tired and 
cold, and generally stay seated on their floats for the 
remainder of the trip. 

This change in the behavior of tubers , who tend to 
become more passive as they progress downstream, may account 
for the observed differences in damage to the tributary 
springs. The heavy damage in the Blue Hols, the first 
spring downstream of the entry docks, has been described. 
Mission Springs, about . M- kilomerers (M m.ile) downstream 
from Blue Hole, also sustained heavy damage, as large amounts 
of Sagittaria and Z'izania cover were trampled out in summer 
1378, In contrast, the major springs downstream from Mission 
Springs appear to have been only lightly dam.aged. The 
Devil's Eye, less than 0.4 kilometers (.^ mile) downstream .. 
and on the opposite bank from Mission Springs , showed few 
signs of disturbance, the only exception being some Sagittaria 
trampling in the spring run. Sim.ilarly, Mill Spring, which 



■ ■- ■ni^ 



120 

discharges into the Floodplain Reach, showed little evi- 
dence of tuber impact . 

These differences in damage reflect not only tubers' 
preferences, in terms of the springs they choose to explore, 
but also a downstream trend of increasing fatigue and 
declining curiosity. 

Species Damage in the Middle and Lower Reaches 

Previous discussion showed that overall plant damage is 
greater in the Headsprings Reach than in the Rice Marsh or 
Floodplain Reach when expressed as a fraction of standing 
crop. In Figure 34, a similar approach is used to compare 
species damage in the three reaches. 

The differences in the magnitude of Sagittaria frac- 
tional loss in the upper and lower reaches is striking. 
Note that in the Headsprings Reach, the fractional loss 
of Sagittaria exceeds the fractional recovery rate (the 
fraction of standing crop that can be recovered by regrowth) 
over most amounts of use. In contrast, rhe fractional loss 
of Sagittaria in the middle and lower reaches generally 
remains below the fractional recovery rate over a wide 
range of hourly use. These data suggest that in the Rice 
Marsh and Floodplain Reach , Sagittaria regrowth can generally 
replace the amounts that are torn and uprooted by recrea- 
tional use. Considering that Sagittaria accounts for 
almost 70% of the total cover in the Rice Marsh, it is not 



121 



90 
80- 

(T 70- 

S 

5 60 

in 
in 

3 50- 

_i 

2 40 

O 

g 30 

a: _ 
u. 20 

lO-l 



Sogiltofia liufiiono 



Oi&^^'2s'^b>-^:^^J2>-A-u, r- 



O Hiadspnngi Rtacn 
• Rica Morsn f^eacn 
^ FioodpiQin R>acA 



Fractignoi Ricovwy Rait 



_ _ . , _ i-ttodspnng* 

~— •^—-"-- ^-^ftiCB Marin 

■1 P'nn/1p,.-i„i 



i 100 
o 

Ji eo 
(/) 

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I 40 

z 



Myriopnyllum naleropfiyllum 



Wo. 

V 

o •= 



9 v.^'^ < 

^ , * « 



FrQcnonol Recovvy Ran 
All R«acn»» 



• 7 



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Volisnefig americono 



Froctionol RtcovtfyRcii 

. Rict Morin 

i a 

2— , Fiooflpioin 



200 400 600 800 1000 1200 i400 
USERS (no./hr.) 



Figure 34. Fractional loss and fractional recovery rate 
of Sagittaria , Myriophyllum , and Vallisneria, 



Fractional loss = 



Fractional recovery ■- 



hourly damage (grams) 
standing crop (grams) 

hourly recovery (grams) 
standing crop (grams) 



122 

surprising that, on visual inspection, this reach appears 
to have sustained little damage. 

It is misleading however, tc assume that recreational 
use has no_ impact on the river plants of this area. The 
damage at the Mission Springs which resulted from tuber 
trampling this past summer has already been mentioned. 
Also, data from the plant damage survey suggest that the 
Vallisneria community in this reach may be damaged by summer 
tubers. Recall from the Results section CFig. 13) that the 
amount of Vallisneria netted from the Rice Marsh was dispro- 
portionately large relative to the size of its standing crop. 
By weight, Vallisneria accounted for about 2 5% of the plant 
damage in the Rice Marsh. The standing crop of this species, 
however, constitutes only 5% of the total standing crop in 
this reach. As Figure 3 4 shows, the amounts of Vallisneria 
that are uprooted and torn in the Rice Marsh often exceed 
the recovery rate of this species. Closer inspection shows 
that, over amounts of use ranging from 25 to 300 per hour, 
fractional loss generally remained below the recovery level 
Con a few hours, however, it exceeded that level by more 
than an order of magnitude) . When amounts of hourly use 
exceed 3G0, which is common on weekends, the amount of 
tearing and uprooting consistently exceeds the amount that 
is potentially recoverable by regrowth. 

The low Damage Index of the Floodplain Reach suggests 
that the plant communities of this area lose a smaller frac- 
tion of their standing crops than do the communities of the 



123 

Rice Marsh or Headsprings Reach. Figure 3 M- shows that, over 
a wide range of use, the amounts of species damage in this 
reach do not generally exceed the recovery levels of the 
respective communities. Note that the amounts of torn and 
uprooted Myriophyllum , an important community in this reach 
(35% total cover), remained well below the recovery rate on 
all 2 2 netting hours. The figure also shows that Sagittaria 
(20% total cover) and Vallisneria (10% total cover) damage 
did not exceed, on most netting hours, the amounts that can 
be recovered by regrowth. 

The only visible signs of damage in the Floodplain 
Reach occur in the immediate vicinity of the Wayside Park 
Landing (tuber exit) and on the bluffs at Devil's Den. At 
Wayside Landing, aquatic vegetation has been eroded by tubers 
who trample the bottom in exiting the river. This damage is 
undoubtedly aggravated by heavy day use in this area. 

The above discussion compared, for each reach, species 
damage and recovery during the summer tubing season. In 
terms of year-round recovery, it needs to be emphasized 
that, whereas the rfeadsprings area is subjected to recrea- 
tional trampling both summer and winter (tubers and divers, 
respectively), the Rice Marsh and Floodplain Reach remain 
essentially undisturbed during the winter months. The 
Sagittaria community in the Headsprings Reach cannot replen- 
ish summer losses by winter regrowth, as divers uproot 
colonizing plants. In the middle and lower reaches, hew- 
ever, the Sagittaria community, as well as other important 



121+ 



communities, has considerable advantage in recouping summer 
losses due to the long uninterrupted recovery period in 
winter. Although, for most species, winter production is 
less than that in summer, the several communities that were 
tested did show a net biomass accumulation during the 
coolest months, as has been found for other constant- 
temperature springs and rivers (Odum 1957, Hannan and 
Dorris 1970) , 

Impact of Recreation on the Animals of the River 

Mollusks 

The results from sampling mollusks were not conclusive. 
The relatively large numbers and biomass of snails in one 
of the Headsprings Exclosure samples suggests that protected 
Char a beds may support a more diverse and larger assemblage 
of snails than disturbed beds. Recall, however, that the 
num.ber and biomass of snails taken from a badly-torn bed 
(.Third Dock, No. 6) were not very different from the amounts 
found in less-disturbed areas , excepting the one sample 
mentioned above. These findings suggest that although 
snails may be more abundant in healthy, undisturbed beds, 
they are still able to maintain populations in disturbed 
areas, even those subject to heavy recreational use. A 
review of otKer researchers' findings, as well as our own 
observations 5 shows this to be a reasonable assumption. 



125 

Whitford C1956), working in several. Florida spring 
systems, found that diatoms, a major food source of 
grazing river snails, grow abundantly on the stems and 
leaves of Chara and other aquatic plants. Diatoms, how- 
ever, are not restricted to this substrates. At the 
Ichetucknee COdum's notes. 1951) and in other spring-fed 
rivers CWhitford 1956)',. these ubiquitous algae have been 
observed on sand, limerock, and other inorganic substrates. 
Goniobasis sp . is commonly found on both sand and limerock 
bottoms, including areas of the Ichetucknee channel, which 
have been subjected to recreational trampling. 

In terms of abundance , one would assume that the large 
surface area of Chara and other aquatics would support more 
diatoms, and consequently, more grazing snails, than lime- 
rock and sand surface. It is therefore likely that the 
torn and uprooted plant beds in disturbed areas will support 
a less than optimal abundance of snails, but will be ex- 
ploited to a degree, by grazing snails. 

ArthroDods 

The results from sampling arthropods, unlike the 
mollusk results, suggest that the survival of some arthropods 
may depend on the growth of aquatic plants . A number of 
studies CNeedham 1958, Hynes 197Q) have shown that the 
number and biomass of arthropods found in plant beds are 
generally much, greater than the amounts found in open sub- 
strates, such as sand and gravel. Plant shelter appears 



126 

to be an important factor for the survival of fresh water 
shrimp and other organisms which are subject to heavy 
predation by fish. The results of this study seem to 
support this suggestion; the sample taken from an area 
which had lost most of tis plant cover due to trampling 
sheltered far fewer arthropods , by number and weight , 
than samples taken from less-disturbed areas with greater 
cover. 

Fish 

The fish survey showed that more types and numbers 
of fish are found in a protected area, the Headsprings 
Exclosure, than are found in a disturbed area, the channel 
downstream from the First Dock. This finding likely re- 
flects differences in the availability of food and shelter. 

On inspection, it is readily apparent that the channel 
protected by the exclosure supports a more vigorous and 
diverse plant growth than does the trampled channel below 
First Dock. As previously suggested, the loss of cover in 
disturbed areas may deplete populations of shrimp, cray- 
fish, and other aquatic arthropods which are importanr 
components in rhe diets of many fish (Hynes 197Q). The 
loss of plant cover, however, is detrimental not only by 
reducing available food: some species appear to be direct- 
ly dependent on plant shelter, while others, which forage 
in the open, require shelter for rest periods or for 
breeding. An example of the former is the py^my sunfish. 



127 



Elassoma evergladei . This fish was often found inside 
plugs of Chara which were sampled for invertebrates. 
Pygmy sunfish are rarely observed in the open (Hubbs 
1943 , noted the same at Silver Springs) , and appear to 
require a dense growth of plants. 

The Carrying Capacity for Recreation 
The following discussion summarizes the supporting 
evidence for the use limits given in Table 6. Because a 
carrying capacity for recreational use should be defined 
according to specific objectives , I have recommended several 
alternatives where more than one management strategy is 
feasible . 

In addition to recommending user limits, I strongly 
suggest that efforts be made to educate the visiting public 
about the plant and animal life and the impact of recrea- 
tional use on this unique and fragile environment . The 
attitude of the Park visitor is one of the most important 
impact factors. Education will hopefully foster appreci- 
ation and concern, which, combined with use limits, should 
greatly reduce damage to the springs and river. 

Swimmers 

Management ob j ective 1 . One objective would be to 
preserve the plant and animal conmiunities of the Ichetucknee 
River with the stipulation that certain springs, such as 



128 



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129 

the Headsprings and Blue Hole, be set aside from protection 
as designated swiinming areas. 

Given the nature of the objective, I do not see a need 
to place a limit on the number of swimmers . 

Swimmers are a minor recreational component at the 
Ichetucknee Springs , in terms of both numbers and percentage 
of total use. In winter, less than 15 swimmers per day use 
the resource. In summer the amount increases, but does not 
generally constitute more than 15% of total use, or about 
150 per day. 

Swimming and the trampling that accompanies it appears 
to have a considerable impacx on those areas where it occurs, 
This activity, however, is generally confined to Headsprings 
and Blue Hole areas, and does not, therefore, constitute 
much of a disturbance to the rest of the river. 

Management objective 2 . A second objective would be 
to restore plant cover in areas that are badly degraded, 
including the Headsprings area. Blue Hole, and Wayside Park 
Landing. 

To permit recovery, I recommend that no swimmers be 
allowed in restoration areas. 

Swimmers, by trampling the bottom, tear and uproot large 
amounts of aquatic plants and disturb invertebrates and 
nesting fish populations . If plant restoration is attemp- 
ted, either by planting or allowing present beds to expand. 



130 

swinuners will have to be kept out of the area. Several 
important findings on plant regrowth are pertinent. One 
is that young and/or small colonizing plants of such species 
as Sagittaria and VaTli sneria , which spread by runners, are 
easily dislodged. The second is that in badly damaged ■ 
areas, where the substrate has been trampled clean, regrowth 
will primarily occur by the lateral outgrowth of plant beds 
which survive along the edges of such disturbed areas. 
This type of regrowth, where not aided by buried fragments, 
is slow. The maximum outgrowth of Sagittaria in the Run 
Cage in Blue Hole was 5 centimeters over a 3^-month period 
in summer. The Chara bed in the Second Dock Exclosure ex- 
panded, at a maximum, a little over 30 centimeters, or about 
12 inches, over a three-month period. Considering the large 
amount of disturbed bottom in areas such as the Headsprings 
and Blue Hole, several years will be required for the natural 
regeneration of cover that has been lost by trampling. 

Canoeists 

Management objective . A general objective would be to 
maintain present levels of plant cover in the springs and 
river . 

On the basis of research results and personal obser- 
vation of canoeing impact, I do not see a need to place 
restrictions on this activity. 

Although the Ichetucknee is a popular canoeing park, 
the num.bers of paddlers , relative to amounts of ether types 



131 

of users, is small. The maximum number of canoeists ob- 
served in our survey was 6 5 in a four-hour period on a clear 
January day. A larger number has been recorded, but rarely 
exceeds 100 per day. 

Canoeists generally have little impact on the plant 
communities of the river and springs. On the busiest day 
sampled (65 in four hours) only 5 dry grams, or about 1 
pound wet weight of plant material was netted. Underwater 
observation showed that canoes disturb only the surface of 
plant beds, causing very little breakage and practically no 
uprooting of submerged plants. 

Divers 

Management objective 1 . One objective, applicable to 
diving, would be to permit a slow gradual recovery of the 
Blue Hole and other areas that are disturbed by "this activity, 

To meet rhis objective, I recommend that a limit of 12 
divers per hour be implemented. 

The combined results of the winter plant damage survey 
and experimental growth plots showed that at a level of 5 
divers per four hours , the amount of Sagittaria uprooted by 
divers is about equal to the am.ount that can be replaced by 
regrowth. Because diver damage increases exponentially, and 
because congestion is an important factor in accelerating 
impact, I recommend that a strict hourly limit be imposed 
on diving. The figure of 12 per hour assures that there 
will be no excessive crowding in the Blue Hole and that no 



132 



more than 48 divers will use the resource in a given four- 
hour period. 

Although we did not monitor diver damage in the middle 
and lower reaches of the river (most diving activity is 
limited to the Headsprings and the Blue Hole areas), I feel 
that the recommended number, combined with scheduling and 
registration, would limit some of the types of damage that 
have been reported from the Rice Marsh and Floodplain Reach. 
Such activities noted by myself and other observers include: 
— digging in both soft and hard substrates (sand, 
mud, and limerock) in search of marine and 
terrestrial fossils. 
— uprooting aquatics for personal use in 
aquaria or for the tropical fish trade. 
— digging in and around the boils in the river 

and springs . 
Although the recovery rate of Sagittaria is much more 
rapid in summer than winter (a full order of magnitude in up- 

9 

rooted plots: about 0.03 grams/m /day in winter; about 0.3 

2 
grams/m /day in summer) , the suggested limit would permit 

some recovery during the summer and still provide diving 

recreation . 

Management objective 2 . Although the limit that was 
recommended under objective 1 would permit a gradual recov- 
ery, the Department of Natural Resources may want to restore 
badly-damaged areas in The shortest time possible through 
natural recolonization . 



133 



To achieve this objective, Park management should 
completely restrict diving in these areas. 

The reasons that were given for restricting swimmers 
from restoration areas apply here also, but more strongly. 
It has been emphasized that young, colonizing Sagittaria 
plants are easily dislodged from the substrate. During the 
diver damage survey, we netted a disproportionately large 
number of small, colonizing plants. Inspection of the Blue 
Hole area showed that divers were trampling back new growth 
from the edges of surviving beds . 

The recolonization of disturbed areas that have been 
trampled clean is a relatively slow process . Assuming a 
maximum rate of lateral outgrowth of about 2 centimeters 
per month (based on cage growth), at least three years' time 
will be required for Sagittaria to cover about 80% of the 
channel and pool at Blue Hole (present cover is about 40%). 
Restricting diving during this recovery period would enable 
colonizing plants to develop deeper root systems and to 
accumulate a protective cover of sediment. 

Tubing 

Management objective 1 . One objective for managing 
tuber recreation would be to maintain the present diversity 
of plant and animal life and to prevent the further deterio- 
ration of badly-eroded areas. 

To achieve this objective, I recommend a limit of 10 
tubers per hour. 



131+ 



Damage in the Headsprings Reach is about twice that 
in the Rice iMarsh and about four times that in the Flood- 
plain. I strongly suggest that the carrying capacity be 
based on that level of use at which the most vulnerable 
communities, those of the Headsprings Reach, can recover 
by natural regrowth the material that is damaged by tubing. 
Limiting tuber use on this basis should assure the protec- 
tion of all plant communities on a spring-wide basis, and 
additionally, maintain diverse habitats for breeding animal 
populations . 

A review of the data from the plant damage survey, 
experimental growth plots , and other related research sug- 
gests that when amounts of hourly tubing exceed 100, the 
damage caused by trampling, jumping, and pulling is signi- 
ficantly greater than the amount that can be recovered 
hourly. The species which appear to be most vulnerable 
possess weak stems and shallow root system.s . These include, 
in fact, most of the planr species in the river and springs, 
but particularly Chara , Myriophyllum , Ludwigia , Nasturxium, 
and CeratODhyllum . Of the plants listed above, three, 
Ludwigia, Nasturtium , and Ceratophyllum , are found in small 
amounts in both the Headsprings Reach and the lower reaches. 
This feature, combined with their fragility, considerably 
accentuates the impact of tubing on these communities. The 
trampling thar accompanies heavy use results in large losses 
of cover; the loss of Ceratophyllum cover was estimated to 



135 



be as high as 8% , and that of Ludwigia and Nasturtium about 
2% on busy weekend days when hourly amounts of tubing con- 
sistently exceed 100. 

Although these three species showed some winter recov- 
ery, there are many areas of the Headsprings Reach, espe- 
cially those which have been thoroughly trampled, that 
exhibited very little regrowth. 

The amounts of Sagittaria , Zizania , and Chara that are 
damaged by tubers do not constitute as large a percentage 
loss, but do, however, lead to serious degradation of these 
communities . Our data on Chara damage and Zizania recovery 
are not adequate for analysis, but we do have good informa- 
tion on both the recovery rates and damage rates of 
Sagittaria . If the amounts of Sagittaria damage are aver- 
aged over various ranges of use, 0-100, 100-200 tubers per 
hour, etc., one finds that in the range of G-IQO tubers per 
hour, about 75% of the damage can be recovered by hourly 
regrowth; in the 100-200 range, about 56% of the damage can 
be recovered; and in the 20 0-300 range, only 2 0% of the 
damaged material can be recovered. I feel that the 7 5% re- 
covery level is the maximum that can be sustained without 
causing further deterioration of this community. Winter 
regrowth should be able to restore the Sagittaria that is 
damaged in summer under the sustained use of 0-100 tubers 
per hour . 



136 

Perhaps the strongest support for the limit I have 
recommended comes from the data of June 14, a quiet weekday 
when amounts of hourly tubing remained below 10 for five of 
six collecting hours (the am.ount for the second hour was 
136). The material that was netted over six hours weighed 
about 210 grams, which is about equal to the average hourly 
amount that was netted on Saturday, May 21, when levels of 
tubing activity ranged around 2 00 per hour for five of six 
collecting hours (75 tubers were recorded for the last hour). 
On June 14, hourly Sagittaria damage exceeded the hourly 
recovery rate on only one of the six netting hours, and that 
was by less than a factor of two. On May 21, the hourly 
amounts of Sagittaria damage were greater than the recovery 
rate during all hours of collection, and, in fact, exceeded 
that level by a factor of eight on the busiest hour (25 8 
tubers) . 

We also noticed on June 14 that the water remained fair- 
ly clear over most of the netting nours ; on busier days, 
the water is nearly opaque with sediment stirred by tubers. 
The deposition of this sediment on plant surfaces, which is 
so conspicuously evident in the Sagittaria beds of the Blue 
Hole pool, undoubtedly diminishes the amount of light that 
reaches photosynthetic tissue. I believe that limiting 
tuber use to 100 per hour will not only result in healthier 
plant beds , but will also provide a more satisfactory experi- 
ence for the user. 



137 

Management objective 2 . A second objective, one which . 
I think should be given serious consideration, would permit 
the recovery, in the shortest time possible, of the upper 
reaches of the river. 

It would be necessary to restrict tubing from the Head- 
springs Reach to achieve this objective. 

The upper reaches of the river, including the Head- 
springs, Blue Hole, and Mission Springs, have lost large 
amounts of plant cover and are badly eroded. To permit the 
natural recovery of these areas I suggest that: 1. no tubing 
be allowed in this area and 2. that the fenced exclosure 
below the Headsprings be retained indefinitely as an up- 
stream source of plants for downstream recolonization (I 
recommend the continuation of this exclosure under any 
management plan) . 

One solution to the recommended restriction would be to 
move the enrry point for tubers downstream to a wider and 
deeper launching spot. One should not anticipate, however, 
that a wider and deeper entry area could sustain more than 
10 Q tubers per hour, as recommended under management 
objective 1. 

Analysis of the damage survey data showed that tuber 
impact is not directly related to such morphological charac- 
teristics as river widrh and depth. It appears that user 
behavior, which changes markedly over the course of the 
river, may be a more important factor. The impact of 



138 

excessive trampling and destructive fooling which is so 
prevalent in the Headsprings area, is undoubtedly inten- 
sified by the shallowness and narrowness of this reach. 
Deeper water and greater widths, however, do not necessarily 
reduce tubing impact, but may serve only to direct it to 
shallow shoals and to the edge of the channel. This aspect 
of tuber impact is amply demonstrated in the Blue Hole, 
where strong flow and deep water in the center of rhe channel 
discourage most tubers from swimming or paddling up the run. 
Instead, they head to the edge and tramp out the banks and 
plant beds there, leaving the growth in the center inxact. 

Similarly, the shoals, shallows, and springs of the 
downstream reaches could well be subject to the severe 
trampling that has led to the deterioration of the Head- 
springs Run and Blue Hole. 



LITERATURE CITED 



Arber, A. 1920. Water Plants, A Study of Aquatic Angio - 
sperms . University Press, Cambridge, England. 

Bishop, A. B., H. H. Fullerton, A. B. Crawford, M. D. 

Chambers, and M. McKee . 19 74. Carrying Capacity in 
Regional Environmental Management ^ EPA /' 600/ 5-7'4-021, 
Washington DC. 

Burden, R. P., and P. F. Randerson. 19 72. Quantitative 
studies on the effects of human trampling on vegeta- 
tion as an aid to the management of semi-natural areas 
J. Appl. Ecol. 9: 439-4 57. 

Deagan, K. A. 1972. Fig Springs: the mid seventeenth 

century in north-central Florida. Hisrorical Archae- 
ology 6 : 23-46 . 

Douglas, R. W. 1975. Forest Recreation . Pergamjnon Press, 
Elmsford, M. Y. 

Ferguson, G. E., C. W. Lingham, S. K. Eove , and R. 0. 

Vernon, 1947. Springs of Florida . Geol. Bulletin 
No. 31, Tallahassee, Florida. 

Gibbens, R. P., and H. F. Heady. 19 64. The Influence of 
Modern Man on ^ the Vegetation of Yoseinite Valley . 
Manual 36, Univ. of Calif., Div. Agric. Sci., Berkeley . 

Hannan, H. H., and T. C. Dorris. 1970. Succession of a 

macrophyte ccmmuniry in a constant temperature river. 
Limnol. Oceanogr. 15: 44 2-45 3. 

Haslam, S. M. 197 8. River Plants, the Macrophytic Vegeta - 
tion of Watercourses . Cambridge University Press, 
Cambridge ." 

Hubbs, C. L., and E. R. Allen. 1943. Fishes of Silver 

Springs, Florida. Proc. Fla. Acad. Sci. 6: 110-130. 

Hynes, H. B. M. 19 70. The Ecology of Runnin g W aters . '^ 
Univ. of Toronto Press, Toronto. ' 



13 9 



lUO 

Krebs, C. J. 1972. Ecology, the Experimental Analysis of 
Distribution and Abundance . Harper and Row, New -York. 

LaPage, W. F. 1967. Some observations on campground 

trampling and ground cover response. U.S.D.A. Forest 
Serv. Res. Pap. NE-68. 

Lime, D. W., and G. H. Stanky. 1971. Carrying capacity: 
Maintaining outdoor recreation quality. Recreation 
Symp. Proc, pp. 174-184. Northeast. For. Exp. Sta., 
Syracuse, N. Y. 

Lucas, R. C. 196 3. Wilderness perception and use: the 
example of the Boundary Waters Canoe Area. National 
Resources Journal 3: 394-411. 

Meyer, F. W. 195 2. Reconnaissance of the Geology and — 
Ground VJarer Resources of Columbia County, Florida . 
Fla. Geological Survey, R. I . No . JQ~. 

Needham, P. R. 1938. Trout Streams . Comstock, Ithaca, 
N. Y. 

Odum, H. T. 1957. Trophic structure and productivity of 
Silver Springs, Florida. Ecological Monographs 27: 
55-112. 

Outdoor Recrearion Review Commission. 1962. The Quality 

of Outdoor Recreation as Evidenced by User Satisfaction , 
ORRRC Srudy Report No. 5, U. S. Gov. Printing Office, 
Washington DC . 

Rosenau, J. C, and G. L. Faulkner. 1974. An index to 
springs of Florida. U.S.G.S., Map Series No. 63, 
Tallahassee, Florida. 

Schoefield, J. M. 1967. Human impact on the fauna, flora, 
and natural features of Gibraltar Point. The Nature 
Conservancy, Monks Wood Symposium 3: 106-111. 

Sculthorpe, C. D. 1967. The Biology of Aquatic Vascular ' 
Plants . Arnold, London. 

Stanky, G. H. , and D. W. Lime. 1973. Recreational Carry - 
ing Capacity: an Annotated Bibliography . forest 
Service, iJ.S.D.A., General Technical Repcrx, INT-3. 



T 



arver, D. P., J. A. Rodgers , M. J. Mahler, and R. L. Lazor 
^-'^3- Aquaric and Wetland Plants of Florida . Bureau 
of Aquatic Plant Research and Control, Florida Dept . 
of Nat. Res., Tallahassee, Florida. 



Ill 



Wagar, J, A, 1964. The Carrying Capacity of Wildlands for 
Recreation . For. Sci. Monographs 7 , Washington, DC. 

Whittford, L. A. 1956. The coiiununities of algae in the 
springs and spring streams of Florida. Ecology 37: 
433-442. 



APPENDIX A-1 
PERCENTAGE DRTiVEIGHT OF NETTED PLANTS, 
PALNT DAIvIAGE SURVEY, SUIMIER 1978 

Netted plants were sorted by reach, species, and 
type of damage (leaf fragment or uprooted clump) 
then drained on screens (one hour) and weighed. 
For each category, subsamples of drained Dlants 
were oven-dried ( 70OC ) to constant temperature. 
If there were no significant (5%) differences 
between reaches, a mean for all subsamples of a 
species and damage type was determined^. 



Species 



3agittaria tairziana 
leaf fragments 
uprooted clumps 



Zizania aquatica 
leaf fragments 
uprooted clumps 



Vallisneria americana 
leaf fragments 
uprooted cliamps 

Chara sp. 



Jl^iophyllum 
heterophyllijm 



[jud^;iagia rei^ens 



Ceratcphyllum 
demersuE 



H.S. 



H.S. 



Reach 



H.S., R.M., 
H.S. 

R.M. 



H.S., R.M., 
H.S. 



R.M. 



F.P. 

F.P. 

F.P. 
F.P. 



R.M. , 
R.M., 



P. 
P. 



F.P. 



F, 
H.S., R.M., F, 



H.S., R.M., F 
Nastur-i^jm officinale E.S., R.M., F, 



,P. 
.P. 

P. 
P. 



Number of 
Sub samples 



1^ 
o 
5 
o 



10 
4 



12 
12 



5 
6 



5 
5 

10 



Mean Dry 

Weight 

(% of f.w. f 



+ l.A^ 



9 


.3 


+ 





Q 


11 


.1 


+ 


1 


.0 


9 


.5 


+ 


2 


.2 


3 


.1 


+ 


1 


.4 


10 


.0 


~ 





.9 






+" 


o 

-c 


.6 


8 


9 


+ 


1 


3 


10 


9 


+ 


2 


1 


1 ^ 


Q 


+ 


p 





15. 


c 


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1 




15. 


2 


+ 


1. 


5 


10. 


2 


+ 


0. 


6 


9. 


6 


+ 


0. 


6 



13.7 + 3.3 



12.9 



1 =, 



142 



APPENDIX A-1 
C Continued } 



143 



Species 



Reach. 



Mean Dry 
Number of Weight 
Subsamples (_% of f.w, f' 



Pistia stratoites 



Cicuta inaculata 



Fontinalis sp. 



F.P. 
H.S., R.M., F.P. 
H.S., R.M., F.P. 



5 6.4 ^ 0,3 
5 5.7+0.2 
5 U.9 + 1.1 



f.w. = freshweight. 



H.S. = Headsprings Reach, R.M. = Rice March, F.P. = Floodplain Reach 
'Standard deviation. 



APPENDIX A- 2 

RELATIONSHIP OF CLUMP BIOMASS AND 
LENGTH OF LONGEST LEAF, Sagittaria kurziana 



l.6i 



Sagittaria kurziana 




50 



20 30 40 50 60 
LENGTH OF LONGEST LEAF 



70 



80 



The relationship of weight in grains (y) to longest leaf 
length m centimeters (x) is described by an exponential 
equation: y = 0.02e°-^^^ (r^ = 0.79). This equation was 
used lo estimate clump recovery (biomass) in uprooted plof^ 
where harvesting was not possible. 



144 



APPENDIX A- 3 

RELATIONSHIP OF LEAF WEIGHT 
AND LEAF LENGTH, Sagittaria kurziana 






X 
(9 






0.30i 



0.25- 



0.20 



0.15 



0.10- 



0.05-i 



/-;» 



^^■ip'' 






10 20 30 40 50 

LEAF LENGTH (cm.) 



60 



70 



The relationship of weight in grams (y) to length 
in centimeters (x) is described by an exponential 

equation: y = 0.00i+e°-°^^ (r^ = 0.81). This equation 
was used to estimate leaf recovery (biomass) in cut 
plots where harvesting was not possible. 



145 



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APPENDIX C 
BICMSS OF AQUATIC PLANTS OF THE ICHETUCKNEE RIVER 

The subheadings under species names indicate 
that portion of the plant which was sampled. 
^Vhere more than one sample was obtained, the 
table lists mean dry weight and standard 
deviation. 



STJecies 



Sample Mean 
Date Number of Size Dry Weight 
Sampled Samples (m2) (g/m2) 



Sagittaria loirziana 



Leaves 


2-20-28 
6-13-78 


Leaves, Stems 
and Roots 


2-20-78 
6-13-78 


Zizania aauatica 
submerged 




Leaves 


10-12-78 


Leaves, Stems 
and Roots 


10-12-78 


Zizania aauatica 




emergens 




Leaves, Stems 
and Roots 


10-12-78 


Cicuta macuiata 
floating mat. 




Leaves, Stems 
and Roots 


10-12-78 


Ceratophyllum demer 


sum 


Leaves and 
sterns^- 


10-12-78 


Chara sp. 





Above ground 



2-; 

7_ 



:5-78 
7-78 



7 
3 

3 
3 



2 

1 



0.125 


503.2 + 


63.5 


0.125 


692,0 + 


81.6 


0.125 


536.8 + 


31.6 


0.125 


1001.6 + 


92,0 



0,25 59.6 + 40.2 

0,25 186.2 + 86, 1 



0,25 568.8 



0,25 662.0 



0.0625 



67.2 + 18,1 



2 


0,625 


961,6 + 244.8 


2 


0.625 


996,8 + 18,4 



154 



APPENDIX C 
( Continued ) 



155 



Species 



Ludwlgia repens 
Above ground 







Sample 


Date 


Number of 


Size 


Sampled 


Samples 


■ (in2) 



2-18-78 



K^Tiophyllum heterophyllum 
Above ground 2-22-78 

7- 7-78 

Nasturtium officinale 

Leaves, Stems 10-12-78 
and Roots 

Vallisneria americana 



Leaves 



8-15-78 



Leaves, Stems 8-15-78 
and Roots 



2 
2 



1 
1 



0.125 



0.125 
0.125 



0.0625 



Mean 

Dry Weight 

(g/in2) 



76.8 



37.5 



169.6 + 18.6 
293.6 + 17.6 



99.2 + 13.6 



0.250 464.8 
0.250 688.8 



Ceratophyllum demersuLi does not possess roots. 



APPENDIX D 
STANDING CROP OF AQUATIC PIANTS IN THF^E REACHES 
OF THE ICHETUCKNEE RI7ER 

Standing crop values were obtained by multi- 
plying mean biomass (g/m^) times cover value 
(m2), which was determined by planimetry of 
the aquatic plant communities map (Fig. 6). 



Species 


Headsprings Reach 

Cover^- St. Crop 

(in2) (Kg) 


Rice 
Cover V 
(m2) 


I-fersh 
3t. Crop 
(Kg) * 


Floodplain Reach 

Cover St. Crop 

(m2) (Kg) 


Sagittaria kurziana 


622 


623^ 


7066 


7080 


2475 


2477 


Chara sp. 


369 


368 


1977 


1971 


3479 


3469 


Zizania aquatiea 


450 


284 


2152 


400 


61 


11 


JV^iophyllum 
hetercphyllura 


66 


19 


660 


194 


4190 


1232 


Vallisneria americana 








807 


556 


1231 


848 


Ludmgia repens 


57 


4 


10 


1 


20 


1,5 


Nasturtiijm officinale 


39 


4 


13 


1 


23 


2.3 


Ceratophyllum demersum 19 


1 


+13 


+ 


+ 


+ 


Cicuta mac'olata 


230 


152 


+ 


+ 


+ 


+ 


Fontinalis sv. 


+ 


+ 


+ 


+ 


+ 


+ 



Total Cover 
or Standing Crop 


1,872 


Unvegetated Area 
(in2) 


4,228 


Total Area 
of Reach (m2) 


6,100 



1,455 



12,685 10,203 11,479 8,041 



8,415 



21,100 



40,721 



52,200 



"Cover was measured in winter. Summer values, particularly in the heavily 
trampled Headsprings Reach, would be less. 

■*- indicates that a species is present, but its area/cover not measured. 



156 



APPENDIX E 
PLANT COMMUNITIES OF THE ICHETUCKNEE RIVER 



KEY 






Sagittaria 






Ludwigia 






•^ \ 



Zizania 



.;.;.--.;;..yj | 



Nasturtium 



Myriophyllum 




Cicuta 



» d • 
o 




Chara 



'eratoph y i 1 um 



Vallisneria 



Pistia 



Open areas 






The maps show the major plant beds in three reaches of 
Ichetucknee River. Both submerged and emergent beds of 
aquatic plants are included in the map of the Headscrings 
Reach. Only subm.erged beds are shown for the Rice Marsh and 
Floodplain Reach. The Headsurings Reach and Rice Marsh are 
subdivided into 100-meter sections, the Floodplain Reach into 
80-meter sections. The sections are numbered consecutively 
with the upstream end at the top of the page. Certain 
features, such as docks, landings, and springs, are indicated 
to provide location references. In evaluating long-term covei 
changes, it is _ important to understand that: 1. the plant 
beds shift position under natural forces (meandering of 
channel and flooding) as well as recreational trampling, and 
2. there is a margin of error, estimated to be about 10%, 
m both the position and size of the beds shown in the maps. 



157 



HEADSPPINGS REACH 



158 




HEADSPRINGS REACH 



159 





\-- 



lOm 



'^ 



-C^l 



P^ 



RICE MARSH 



160 







:^^ 



(-"J,- 



.H-j^ 









n 



•^7 v^-'A 




lOm 



RICE MARSH 



151 



iOm 



';i' 






J a 



^j 



''^ ^^ 






c^ 









J Jjl 



'J J -Ml, 



(i/" 




,^1 











:m^k 




RICE MARSH 



162 







/ ' ' / ' / 







', ',, ',' "',r<,,'',/f\ 
















mm 

'/y///<X-:- 



RICE MARSH 



163 




RICE MARSK 



154 




RICE MARSH 



165 





lOm 



FLOODPIAIN REAQI 



166 




FLOODPMIN REACH 



167 




FLOODPIATN REACH 



168 




FLOODPLAIN REACH 



169 



iCm 





FIOODPLAIN REACH 



170 




FLOODPMIN REACH 



171 





r-\ 




FLOODPLAIN KEACH 



L72 




FLOODPIATN REACH 



173 



' ' 


a • 


• < 




a 


» 




9 


( 


./ 


» 


^ 




FLOODPLAUJ REACH 



174 






FLOODPIAIN REACH 



175 




WAYSIOE 
LAHOMG 



'c^ 



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Q 




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\ ■■ 


1 f * 




:\. \ 



BIOGRAPHICAL SKETCH 



; ,»«, ■-•- .V 



Charles Hill DuToit was born in Andover, Massachusetts, 
on June 22, 1947. He received his elementary and secondary 
education in the public schools of Winchester, Massachusetts, 
and was awarded a diploma in 1965. \--'-. 

Charles majored in the social sciences as an under- 
graduate and received a Bachelor of Arts in sociology from 
the University of Massachusetts in 19 72. Subsequent to 
graduation, he developed a strong interest in the natural 
sciences, and, in 19 73, started part-time studies as a 
post-graduate biology major. . - ■ .■ ' 

In May, 19 75, Charles married Marilyn Leigh Pichler 
of Miami, Florida. In fall, 1976, he enrolled at the 
University of Florida as a graduate (M.S.) student in 
botany. 



176 



I certify that I have read this study and that in my 
opinion it conforms to acceptable standards of scholarly 
presentation and is fully adequate, in scope and quality, as 
a thesis for the degree of Master of Science. 



^^ijolin Ewel, Chairman 
Associate Professor of Botany 



1 certify that I have read this study and that in my 
opinion it conforms to acceptable standards of scholarly 
presentation and is fully adequate, in scope and quality, as 
a thesis for the degree of Master of Science. 



,1 



V 



kv\.<?,\ Lugo -* 

Associate Professor of Botany 



I certify that I have read this study and that in m.y 
opinion it conforms to acceptable standards of scholarly 
presentation and is fully adequate, in scope and quality, as 
a thesis for the degree of Master of Science. 






ink G. Nordlie ^ 
Professor of Zoology 



Frank G. Nordlie 



This thesis was submitted to the Graduate Faculty of the 
Department of Botany in the College of Liberal Arts and 
Sciences and to the Graduate Council, and was accepted as 
partial fulfillment of the requirements for the degree of 
Master of Science. 

August, 19 79 



Dean, Graduate School 



UNIVERSITY OF FLORIDA 



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